EDIT on the part OUTPUT AND RUNTIME, added data of tailcap measurement provided by contactcr
Hi BLF!
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: Page Not Found - Aliexpress.com
No Package: Page Not Found - Aliexpress.com
This flashlight is the updated version of the Z821, which is – apparently - sold in Fasttech (they have no stock, I wonder why :person_facepalming: )
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!
GENERAL SPECIFICATIONS
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
OTHERS:
- Constant Current Drive
NOTE: these are the specs as provided by the manufacturer!
THE PACKAGE, FLASHLIGHT & ACCESSORIES
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 
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
This is how the flashlight looks like when dismantled. Only the MCPCB/led and the driver weren’t taken out.
So:
- 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 :weary: 
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 :person_facepalming:
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
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 
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 :+1:
As the other lights I have, this one came with a nice protective pouch to carry the flashlight. I like it
USER INTERFACE
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
OPERATION:
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
NOTES:
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
OUTPUT AND RUNTIME
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 |
NOTES:
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 :person_facepalming: )
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
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 )
Vs my “Lego” of OTR M1 (down tube/tail) and OTR i3 (upper tube/head), a thin 16650 zoomie flashlight :student:
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:
40m
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:
16m:
45m (trees):
Close range (Z-OUT) vs 100m Distance, farthest tree (Z-IN)
OVERALL APPRECIATION
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 I wish people would chose better zoomies as this one instead of those cheapo bulky ones, but…to each its own…
Keep up the good work! 
If you folks have any question or comment, let them come :+1:
