“REVIEW”: On The Road Z821 - Zoomable – 1x18650 – 940 lumens [Pic Heavy]

EDIT on the part OUTPUT AND RUNTIME, added data of tailcap measurement provided by contactcr


This is my review of the On The Road Z821 flashlight!

I bought this flashlight in the “package” version in the end of June and it arrived in the end of July. The OTR Z821 is also sold in the “no package” version. Here are the (non affiliated) links for On The Road store at AliExpress:
Package: https://www.aliexpress.com/item/4001177537842.html
No Package: https://www.aliexpress.com/item/4001199114321.html

This flashlight is the updated version of the Z821, which is – apparently - sold in Fasttech (they have no stock, I wonder why :FACEPALM: )

There are no internet reviews so far, as far as I know, and here on BLF the other considerations on this flashlight are on this thread.

So, let’s start this!

Body Colour: Matte “Chocolate”
Material: Aluminium
Emitter: XML2 U3 1A (Cool White)
Lens: Glass, Optical Aspheric (non AR Coated)
Battery: 1 x 18650
Switch: Reverse Clicky Switch
Reverse Polarity Protection: Yes
Low Voltage Warning: Yes
Max runtime: 160 hours
Max beam distance: 240m
Max output: 940 lumens
Candela: 14500 candela
Waterproofness: IPX6
Impact resistance: 1m


  • Constant Current Drive

NOTE: these are the specs as provided by the manufacturer!


Like the recently received and reviewed On The Road 311, the On The Road Z821 arrived in a “new package” from OTR, a white box with some information about the flashlight on its sides. Just to inform, the previous ones were square cardboard boxes, also OT branded. This one is nicer for a gift, IMO :wink:

Along with it arrived the box for the battery charger, which comes in separate.

The “package” version of this light contains: On The Road Z821 flashlight, OTR branded pouch, OTR branded lanyard, a battery charger, a USB to USB-C charging cable, an unprotected 18650 3100mAh 3.7V 11.5Wh Li-Ion OTR branded battery, User Manual, 2 spare o-rings.

Both the outer and the inner boxes were sealed with an adhesive sticker!

The On The Road Z821 is a zoomable flashlight!
Yeah, I know many people here are not fans of “zoomies”, I also know that many people out there think that zoomies (specially those G700) are the best of the best of the best!

I am somewhere in between: I do like zoomies, I have some, I’ve gifted some, one of the lights that brought me into flashaholism is a zoomie light (Nebo Micro Redline), but I also know that they have many cons, and I admit that.

Despite that, I always wanted to have some nice, compact, push-pull zoomies, capable of fitting into a pocket light a “normal” EDC flashlights.
That is why got the OTR i3 some time ago, and that is why I bought the OTR Z821!

In my opinion, despite the cons that can be pointed out to zoomies, this is a good one!

It has “chocolate tablet” pattern knurling, just as other OTR lights, which is not very common on other brands.

In one side, it has the OTR logo engraved, while on the other it has the model engraved.

While extended / zoomed in, it can be seen a “1.5cm” scale on the battery tube, along with the flashlight serial number.

Unlike the old Z821 model, the head has no engravings, but it has some “teardrop” grooves and also an horizontal groove slightly below the bezel.

The bezel is a shinny one, but I am not completely sure if it is stainless steel. It is a bit “grainy” not completely smooth. It has no grooves (unlike the i3, M1 or M3 Pro).

Looking at the size and weight, well, this is not the lightest flashlight, but it is not heavy. Maybe slightly heavier than a Convoy S2+.
Also, in terms of length, being this an 18650 zoomable flashlight, I believe it is quite “compact” in the Zoomed out form :wink:

This is how the flashlight looks like when dismantled. Only the MCPCB/led and the driver weren’t taken out.

- bezel

- o-ring around the bezel

- glass aspherical optic

- thick “broken-on-purpose” o-ring

- smooth ”reflector”

- brass pill with an o-ring around it,

- 16mm x 1m aluminium PCB with XML2 U3-1A Cool White Led

- white plastic 5050 gasket

- driver with small flexible spring, pressed fit into a brass ring, which is fit into the pill’s bottom

- ”head” structure

- thin o-ring (that sits between the head and the tube and helps: a) sliding the head, b) “water proofing” (?) )

- batery tube with an o-ring (and with square or trapezoidal threads)

- brass retaining/housing structure/ring

- reverse clicky switch mounted on an OTR branded PCB with a thin but strong spring

- aluminium spacer (above the switch)

- rubber tailcap

  • “tail” structure, with 2 lanyard holes

I’m tired :TIRED: :smiley:

Looking to the head.

The bezel can be removed easily by pressing the light against your hand (with gloves, preferently).

The ”reflector”…this was a difficult one! I scratched it a little bit. I advise to use thin tip pliers and not pointy tweezers to unscrew it, in case you wanna reach the led. Also, in case you wanna mod the light and use a ticker MCPCB, remember those “waves” on the bottom of the reflector, as they may cause short circuits !!

The optic of the Z821 aspherical. Below it sits a thick “broken-on-purpose” o ring that I believe it acts as a cushion for the optic an also to allow air movement (through it’s gap). But maybe I am wrong in this assumption…

As said, the Led PCB is 16mm x 1mm aluminium. A larger one can be used in case you wanna mod it!
As for the driver, it is a 17mm driver, that brings OTR newest configurable firmware !!!
The spring is thin but strong, as the inner space needs to be able to take longer and shorter batteries (which it takes).

There is a discussion on this thread (start reading here) about the advantages or not of using brass pills vs aluminium, in case you wanna look.

Be sure to be careful with this thin o-ring between the head and tube. It is very important to keep it lubed for a good sliding and water/dustproofing.

Also, it can be a PITA to put it back in place once it is taken out :FACEPALM:

The tube inner threads, where the brass pill screws in may be a bit harsh in case you take it out often. Be sure to add some lub to make it less grainy.

Going towards the tail…
As mentioned above,a rubber tailcap and 2 lanyard holes, in which you can also put a screw-in pocket clip.
The threads are well cut, trapezoidal I guess, and arrived well lubricated as the o-ring* on this tip.

As for the rest of the structure, I had to use some thin point pliers, putting the tips into the PCB holes to make the structure unscrew. Nothing is glued, but it was really tightened!!

Advancing to the accessories, let’s start by the battery charger.
It is called UC3-PRO, it is supposed to do “smart charge” (whatever that means), and in the back there is an OTR logo in haut-relief.

The source can feed the charger through an included USB to USB-C cable. I don’t know of it can use USB-C to USB-C connection.

Input: DC5V 0.5-3A
Output: 4.2± 0.05 1A
Operating temperature: 0-40ºC

It can charge batteries from 16340/RCR123 batteries up to 18650s. Everything in between in terms of length (not diameter!!! ) can be accepted/charged…
BUT, long-protected-button-top 18650s (like the Wuben red battery below) do not fit!

The charger has red led to indicate charge in process and a blue led to indicate charging complete!!

Being so light and capable to charge 16340s, 18350s, 14500s,10440s and 18650s, this is a good travel charger :wink:

As for the battery included in this package, it is the unprotected flat top ORB1831 / INR18650 / 3100mAh / 3.7V / 11.5Wh / Li-Ion / OTR branded battery in a yellow wrap! I am not sure what can be the original battery below the wrap, but I know it is not a Sony VTC6 :stuck_out_tongue: Maybe it is an LG… !

This is how it fits on the flashlight!

Well, I don’t have much to say about the menu. It is written in Chinese, and I can only get some numbers from there.
As this light was only recently put for sale on AliExpress, being the Chinese market OTR primordial market, I believe they were not looking to make it in English. I hope they will do it soon :THUMBS-UP:

As the other lights I have, this one came with a nice protective pouch to carry the flashlight. I like it :wink:


Although it is not stated in the products page, the box has some information about the UI being configurable.
It is the new OTR configurable firmware which is also present on the OTR 311 flashlight.
It has 3 group modes. Using the brand’s “naming”:

A – Ultra Low > Low > Medium > High + Strobe or SOS or Beacon

B – High > Medium > Low + Strobe or SOS or Beacon [default group mode]

C – High + Strobe or SOS or Beacon

BLINKING MODES always flash/blink in the highest output
STROBE: single frequency
BEACON: flashes maybe each 1.2 seconds
SOS: is quite fast, and then has a 5s pause to restart the new blinking

1 - Turn ON / OFF : full click the tailswitch
2 - Change output levels in any group mode: while ON, tap the tailswitch
3 – Engage/Disengage Strobe: while ON, quick double tap to activate Strobe, and a single goes back to the regular level
3 – Engage/Disengage Beacon: while ON, quick triple tap to activate Beacon, and a single goes back to the regular level
3 – Engage/Disengage SOS: while ON, quick quad tap to activate SOS, and a single goes back to the regular level

The flashlight has memory for the last used mode, except the blinking modes.
However, on Group modes A and B, a quick turn OFF > turn ON (within 3 seconds) will advance to the next level. If the flashlight is OFF for more than 3 seconds, the last used mode will be memorized.

NOTE: really quick full clicks (OFF-ON-OFF-ON…) can activate Strobe, Beacon or SOS.

Perhaps the most “complex” part of this flashlight is on “how to alternate between the group modes A, B and C”.
After contacting the store, here is the answer:

1 – Turn the flashlight ON in HIGH level (in any group mode)
2 – Enter STROBE for 5 seconds or more
3 – Tap to go back to HIGH (1st)
4 – Enter STROBE again (doesn’t matter the time)
5 – Tap to go back to HIGH (2nd)
6 – Enter STROBE again (doesn’t matter the time)
7 – Tap to go back to HIGH (3rd)
8 – Enter STROBE again (doesn’t matter the time)
9 – Tap to go back to HIGH (4th)
10 – Enter STROBE for 5 seconds or more
11 - Turn the flashlight OFF

1 – During this operation, never turn the flashlight OFF or it will “cut” the configuration process.

2 – The initial and final STROBES must really be ON for 5 or more seconds, otherwise the configuration will fail.

3 – The changing between the group modes will start from the default group mode (B), then C, then A, then B… .

4- As pointed out above, and just to be clear, group mode A advances from the lowest to the highest level, while group mode B advances from the highest to the lowest level


As I can’t accurately measure these, I will rely on manufacturer’s information (using their 3100mAh battery and a XML2 U3 led). This will change with different leds and batteries, of course.

UltraLow Low Medium High
OUTPUT 4 lm 150lm 390 lm 940 lm
RUNTIME 160h 11h 4h 1h40m

Assuming that this driver works as the one in the OTR 311:

- the light will flash if the battery is below 5% (I didn’t test this yet. I normally charge the batteries when I feel the light is more dim than usual).

  • fast charging is possible, reaching 90% capacity in 140 minutes. Full charging cycle is around 4hours. (NOT SURE IF THIS IS TRUE, I CAN’T READ CHINESE :FACEPALM: )

EDIT(16th August)

Tailcap measurements
Data provided by contactcr

So…let’s go for a flashlight comparison.

Vs FW3A & Convoy S2+ Desert Tan

Vs some of my zoomies collection :smiley:

Vs Livarnolux 314951 & Livarnolux 314791 (2xAA zoomable flashlights from Lidl)

Vs RovyVon Aurora A23 & RovyVon Angel Eyes E200u (they all arrived at the same time :stuck_out_tongue: )

Vs my “Lego” of OTR M1 (down tube/tail) and OTR i3 (upper tube/head), a thin 16650 zoomie flashlight :GRAD:

Vs the OTR family: M1, 311, Z821, M3 Pro, i3

No PWM on the 4 regular levels.

And let’s take a look at the beam pattern and level’s progression!

This was made at 1m from the luxmeter (set on Lux), just for exemplification purposes!

This is a comparison between the OTR Z821 (left, XML2 U3-1A) and the OTR i3 (right, with Samsung LH351D 5000K 90 CRI). Please note that the i3 is already modded, both the driver (MTN 15mm DD with Crescendo FW), the led, and also the reflector and lens (blackened to avoid artifacts).

Some outdoor beamshots now!
This light, stock, can reach around 200m. I wasn’t able to test it in “pitch black” conditions, but I can assure that it reaches those distances.

The beam, while zoomed in, has some artifacts, namely rings, and the shape or the led is “visible”, which means it is focused to the point (wether it is good or not!).

While zoomed out, the artifacts are less, but there is still one outer ring, almost imperceptible, maybe due to the reflection on the bezel. This can be reduced with some blackening on the reflector, lens, and bezel.

On max, zoomed in:

180m (farthest field)

220m (top house)

210m (house/street light)

That ring I told about when zoomed out.

Direct comparison: Zoomed out > Zoomed in

Close distance:


45m (trees):

Close range (Z-OUT) vs 100m Distance, farthest tree (Z-IN)


I bought this light because I wanted to have a compact 18650 zoomable light! And it was what I got!
The flashlight has modding potential, but it can already be “ready-to-use”, in case you want to.

What I like:

- Overall quality, in particular anodizing and machining!

- Shape, size and compactness, and I’d say elegance, for a 18650 zoomie!

- Accessories included, as you get all you need and more! Well, except the User Manual…

  • Configurable User Interface, because it offers more options of usability.

What may bother me:

- Memory mode, for the group modes with more than 1 level

- Possibility to accidentally activate Strobe when tapping faster to change modes (Beacon and SOS are “more hidden”)

- Long process to alternate between the group modes

  • Some artifacts on the beams (nothing that other lights, zoomable or not, don’t have)

Modding plans?

- led4power driver 4A-6A

- Osram White flat (not sure if W1 or W2) + appropriate gasket

- blackening reflector and part of the optic

- Eventually: forward clicky switch

  • Eventually: screw-in pocket clip

Thanks On The Road store at AliExpress for putting this light on sale :wink: I wish people would chose better zoomies as this one instead of those cheapo bulky ones, but…to each its own… :stuck_out_tongue:

Keep up the good work! :beer:

If you folks have any question or comment, let them come :THUMBS-UP:

Thanks for the terrific review MascaratumB. :beer:

Great and very thorough review! The On The Road Z821 is a good looking flashlight.

So it’s not meant to operate below zero C — which is 32 Fahrenheit, freezing temperature? That sounds pretty strange.

And it’s good up to 40C, which is 104 fahrenheit. Hmmm.

Thanks for your words MRsDNF :wink:

Thank you Neutral Fan :wink:
Yes, it is indeed a good looking and nice hand fitting flashlight!

Thanks for looking :wink:

Well, as far as specs concerns, it is that way :wink:
Maybe it is due to any component inside or something. I will not opent the charger as it is glued/press, no screws. Otherwise I would show how it looks to see if it is anything physical that “hinders” that :+1:

Great review as usual MascaratumB. I am usually not into Zoomies but this seems like a decent one.
I just dont understand the thought behind that not include pocket clip. Even worse, I do not see where to mount one if I want to. Poor design choice I guess.
Dont get me wrong, the including pouch is nice but it wont get much use if I cant carry in my pocket when I need it.

Thanks for reading and for your words Anthony Nguyenn :+1:

About the pockect clip, I will install mine in the lanyard holes , just like a if it was a Convoy S2/S2. The holes distances are relatively similar to an S2/S2 . The screw-in clips sold in Convoy Store (and many other online stores), will fit nicely, I confirmed th distances.
OTR normally includes clips on their lights, but I actually like that this one doesn’t have a groove for the clip, it makes the light more “clean”, if you know what I mean.

The pouch is sweet, but I agree it is not for a quick flashlight draw.

@ Anthony Nguyenn

In the name of flashlight science :nerd_face: :student:

The example I gave:


Mine came with group A default (4 L-H modes w/ hidden strobe, memory enabled)

Bypassed tail measurements:

Sanyo NCR18650GA 3500mAh

UL = 13mA
L = 265mA
M = 732mA
H = 2.60A

Feel free to add to review if you want.

My initial impressions with just a few minutes of handling:

The size is awesome, nice and compact!
Anodizing and machining very good.
Focus appears to be good.
Host warms up quick which tells me thermal path between pill and body is good.
The packaging is very good and everything is sealed as if this light is sold in retail stores. (maybe some Chinese REI type place?)

Given how compact the host is I will have to temper how far I will hot rod this light. I dont think it’s suitable for maxing out a 2mm2 white flat but maybe ~5A is good enough. The springs will have to go when it’s modded, they are quite thin.

Assuming mods go as planned this appears to be a very good 18650 zoom light. Granted it’s a huge leap in price from typical shit zoomies it seems to at least be a huge leap in quality above them too.

Shipping time to US: ordered, 30 June, arrived 15 Aug. I guess Singapore > US transit still a bit slow.

I’m not proud of this soldering and it’s only temporary until I change the driver but I wanted to see what i’m in for. They barely left enough LED wire to even account for the extra 0.5mm MCPCB thickness :person_facepalming:

It goes from about ~15kcd to ~39kcd keeping stock driver and putting 3030 2mm^2 white flat (CSLPM1). I used a 3030 gasket I think I got from intl-outdoor long ago and it’s a perfect fit.

To be continued

contactcr thank you very much for your input on the tail current measurements! I am on the phone, so it will be easier for me to edit post#1 in the computer!

Also, thanks for showing your mod-in-progress! That leap on candela is quite wow, just with the stock driver. I assume a different one will make it rise even more, be it at 5A or more!

BTW, did you have and issue with the MCPCB height vs the “reflector” and the contacts with the solder, or do they stay out of contact?

Also, unless your driver is different from mine, the UI should have Strobe / Beacon / SOS as special modes with 2, 3 or 4 multiple clicks from ON. I wish memory could be configured to stay off… :weary:

Again, thank you very much for sharing your words, mods and measurements :wink: :slight_smile: :+1:
And show us the rest meanwhile :wink:

I’m using a plastic centering ring so its probably half or 1 thread less screwed on but still putting pressure on whole pcb by way of that gasket. Not sure how close it is but I had no problems. For the final assembly I may use kapton tape or may not…

Mine has strobe via double click but came default as the 4 normal modes.

Hard to tell if the .5mm from pcb effects focus or not. It’s pretty defined but this LED has very even die so you can’t look for dots or bond wires to be sure

For me, it’s not really modding unless you break something, so here is tonight’s sacrifice:

I thought I could pry the board out first. Nope (well yes, but not recommended) it’s soldered on the other side of the press fit ring.

Oh well, I took apart a perfectly good modded S2+ to gut the driver and MCPCB. I planned to do it anyways but still I hate taking working lights apart cause more than once I just end up with two not functioning lights. Desperate times since LED4Power is on hiatus.

Filed down and pressed into ring, lightly soldered. Ring then pressed into pill, no solder:

Might as well get that tail spring too:

Gotta have that temp sensor. Sad part is I re-flowed the LED cause I feel more confident doing that (on a 3535 board no less) than transferring the NTC from board to board.

Gasket with side clipped, pretty sure from intl-outdoor. It’s probably not ideal cause the “reflector” (MascaratumB’s word) only screws down about half way. Ideally it would be sanded down some.

Tail wont go on, springs are too long, ugh. Button maybe?

Nope, not enough. Tail has to change too:

It turns out this tail is partly why the light is so compact. The tail legos with an S2+ and if you hold them side by side you can see a few mm difference. This light will likely never fit anything but flat tops. It also explains why I initially thought the original springs were so thin and cheap because they have to fully compress to fit a normal battery.

End result:

I set the driver to around 5.3A and measured 63.4kcd

If OTR is lisenting: add another ~1.5 - 2.0mm to the tail cap and get better springs on both ends.

MascaratumB & Contactcr

Very thorough review and nice mod :+1:

So 63 kcd means that it should be close or hit 100 kcd with WF1… That is good result for such light. It could be better(up to 20%) though if they will ever redesign aspheric lens (larger aspherical surface and smaller lens edge, and current is small aspherical surface and too much of “edge” on aspheric glass) .

Yes this is very rare China light that is usable out of a box(nothing special) but it demands modding for wow effect.
It is bit to expensive IMHO for factory version. But if they will ever learn to properly make the light(not just OTR, most China manufacturers) and that means if you are saving on emitter at least put freaking DTP board into the pill!(why they want to save 0,5$ on DTP board?)

This light should be ofered as a host, and it should not cost more than 15$(even that would be bit to much).

@ contactcr
Thanks again for your input on the modding process :wink:
About the centering ring, that also happens with me on the i3, the “reflector” (IDK how its is called, sorry) doesn’t screw all the way down :zipper_mouth_face: I didn’t have capton, I used electrical tape, even if nor ideal.

On the mod, did you took the retaining ring of the driver out? It seems that it can be taken out of the pill throught those small holes in the side. I’d like to “maintain” the integrity of the original driver, it can be worth to make another mod :wink:

Normally I don’r solder any temp sensor wire to the led MCPCB :smiley: Am I doing it wrong? :partying_face:
Or does it have to do with the type of driver you have?

I’ll put a L4P driver as well, but normally I don’t add those special temp things (I don’t actually know how to work with that :stuck_out_tongue: ), hence my question.

Quite an improvement since the original measurements. A W1 would probably get some more intensity, but the W2 also seems to project the light far away :wink:
Well done :wink:

And BTW, you did a pretty clean job in the mod, I am very messy with this stuff :person_facepalming:

I may need to start thinking about a new spring for the spring, maybe the original is too thin afterall :weary:

@ luminarium iaculator
Thanks for your words! And I hope you are enjoying your light as well.
BTW, did you see the YAGE zoomie light that is pretty similar (although bigger) than this light on AliExpress? It is sold, the complete light for around 7€. It probably has aluminium pill and acrylic lens, and despite being bigger, it still seems a compact zoomie at a nice price :wink:

BTW, this is that YAGE I mentioned above.
(which is more similar to the old Z821)


I did take the ring out eventually. I think using heat/cool and something small and stiff (stainless something) you can pry ring gradually from either side. If I had to do it again I would do it that way and try to push driver out of ring while it’s on hot plate or something.

It’s not necessary to function. L4P driver has temp sensor on driver and also this NTC connection for supported PCB. The MCPCB temp steps down at 115C or something while driver temp steps down sooner, 65C or whatever custom setting. I think it’s a more accurate way to do step down based on MCPCB temp though.

As for how “clean” everything is here is my tip: old toothbrush + alcohol and just dip toothbrush and scrub anything and everything.

Thanks for both replies contactcr :+1:

I guess taking out the ring will be better then. I know thus is their normal setting , so it will be better than pushing the driver from the top.

Also, thanks for the info on the driver/MCPCB temp sensor. All the lights I have with L4P driver don’t have that wire, it is always based on the driver itself. Maybe I’ll give it a try this time :wink:

Ahah, best tip :wink:
But I was also complimenting your solder skills. My wire soldering to the MCPCB, driver and spring can become quite nasty, that not even a toothbrush can clean it well :stuck_out_tongue:

Thanks again for sharing this!

If you try temp sensor make sure mcpcb is populated with that tiny resistor at bottom or else it won’t work

Sure, I will ask led4power to send it with the resistor when he opens the store again :wink: