“REVIEW”: On The Road M4 Turbo – 4 x Nichia 5700K High CRI – 1100lumens – 1x 16340 – USB-C


This is my review of the On The Road M4 Turbo flashlight.

The flashlight was bought in the OTR official store at AliExpress (non-affiliated): https://www.aliexpress.com/item/1005003412158323.html

The flashlight in review has 4 Nichia 219CT 5700K but there are other LED versions (SST-20 6500K, Nichia 219CT 4000K).

Here are some video reviews of this flashlight:
Review or How it works (English): https://youtu.be/wHdPjHDSpPU
LumensLaboratory (Chinese): https://youtu.be/Bm476dGGjfI


Body Material: T6061 Aluminium
Body Colour: “Titanium” colour
Bezel Material: Stainless Steel
Optic: Carclo 10507
Emitters: 4 Nichia 219CT 5700K >90CRI ( others: SST-20 6500K, Nichia 219CT 4000K )
Switch: E-Switch (side)
Batteries: 1 x 16340 Li-Ion / RCR123 / CR123a
In-Built Charger: USB-C
Beam distance: 90 m
Beam intensity: 2050 cd
Water Resistance: IPX6
Impact resistance: 1 m
Reverse Polarity Protection: Anti-reverse battery protection ( Poka Yoke :smiley: )
Low voltage warning: Yes

Driver: Constant Current
Other: Active intelligent temperature control


The OTR M4 Turbo arrives in an OTR branded box with some information about the flashlight on its sides and a photo of the specific model in the front. Curious to see that the emphasis is on the USB-C port and not in the 4 leds :stuck_out_tongue:

The “package” version of this light contains:

- On The Road M4 turbo flashlight

- 16340 700mAh 3.7V 2.6Wh Li-Ion OTR branded battery (unprotected)

- pocket clip

- carrying pouch

- OTR adjustable lanyard

- OTR USB to USB-C charging cable

- user manual

  • 2 spare o-rings

Here I wanted to emphasize that the OTR M4 arrived in a vacuum sealed bag, and that inside it there was the 16340 battery, with a sticker on the negative pole to prevent activation or draining during shipping.

So, what are my first impressions of this flashlight?

- it is small in length

- in diameter it is not so small if compared with less large lights (ex: S1R Baton II)

- it feels good in the hand, and is easily operated

- the beam has some artifacts, given that it has a clear Carclo optic

- the tint is pleasant, though, and I really love these Nichia 5700K LEDs :LOVE:

- it has configurable UI (to some extent) which I really like

- it is a great option for a EDC flashlight!!!

Under a descriptive perspective:

- the OTR M4 is composed by 2 parts: head/tube + tailcap

- the anodizing is what OTR calls “titanium” colour, but it is slightly brownish, which is typical in many OTR flashlights; it is well anodized

- there are no visible imperfections nor machining flaws

- the stainless steel bezel can be removed to access the head (I used a leather glove to make pressure while rotating the flashlight)

- there is no glass lens above the Carclo 10507 TIR optic

- the 4 emitters are disposed in a “Y” position in the copper DTP MCPCB (~2mm thickness)

- in my flashlight, the emitters are 4 Nichia 219CT 5700K >90 CRI that provide a neutral white beam and high colour rendition

- despite this, there are some artifacts due to the type of optic and also the 4th emitter being placed in the centre of the “beam”

- similarly to other lights like this, there is a structural shelf (aluminium), and not a pill

- the “head” structure has some cooling fins on each side

- in the front there is the silicone OTR button where the e-switch is operated

- the e-switch has indication leds (BLUE and RED) which will be mentioned below

- in the back there is the silicone cover for the USB-C charging port, which stays in place well and doesn’t come out accidentally

- below these there is a groove for the pocket clip

- in the “tube” part there is a chocolate tablet knurling pattern, also typical from OTR flashlights

- there are 2 flat parts in each side of the tube, in which there is engraved the logotype and the flashlight model

- before the threads there is a sealing o-ring

- the threads are anodized, square but thin, and arrived lubricated

- from the tube hole it can be seen that the driver has a thin golden spring to make contact with the positive pole of the battery

- the “tailcap” has the same chocolate tablet knurling pattern all around and is flat allowing tailstanding

- on the bottom it has the serial number engraved

- inside there is a spring that is held in place due to its triangular basis

- the pocket clip must be placed with the curve towards the head and tip towards the bottom and it is not reversible

- it can be used to prevent accidental activation by blocking the switch while in place

- the lanyard must be attached to the pocket clip, as there is no lanyard hole in the flashlight body

- the OTR M4 doesn’t take long protected cells nor large cells (ex: Wuben 16340), but it takes button or flat top cells

Lets see some of the above mentioned things “embodied” :wink:


Front and back




Regarding the size and weight, as mentioned this is a small 16340 flashlight with side switch, even if it is not the smallest one (ex: I believe some Olights and the Cyansky M3 are shorter).

Also, even if it is not as slim as other lights, it surely isn’t the largest one (ex: compare with the RovyVon S3 or the Wuben TO10R).
However, it is still a lightweight flashlight!!

Last photo has the cell and the pocket clip!


And now let’s take a look at the accessories it comes with:

This is protective/carrying pouch that OTR normally includes in the “full package” for their lights, eventually made of neoprene or something alike. It has an adjustable closing thread, and I can tell that be it for a flashlight or money, this is a nice pouch :wink:
The pouch also arrived in a vacuum sealed bag!

Although these are 2 accessories, in this case I will join them since that, as mentioned above, there is no lanyard hole in the flashlight body, which means that the lanyard has to be attached to the pocket clip in case one wants to carry it that way.

The lanyard is adjustable, although it only has a “sliding” plastic piece instead of a toggle stopper

As for the pocket clip, it provides good carry and retention, it can only be placed in the groove below the switch (curve up, tip down), and due to this the flashlight can be used as “cap light” . The pocket clip also helps to block the side switch and prevent accidental activation.

The included battery is the On The Road 16340 700mAh 3.7V 2.6Wh Li-Ion (ORB1607). This is a standard unprotected battery from OTR, that seems to be around for many years now. It arrived with a thick black sticker in the negative pole to prevent accidental activations or/and draining during shipping.

As for the user manual, OTR has been improving their UMs and providing information in a better and clearer way. It provides the important information on how to operate the flashlight, including on how to configure the UI!!!
All the other standard information is also provided
(click to see larger photos)

Last but not least, there is a 60cm charging cable included, USB to USB-C, OTR branded.


Although there seems to be some conflicting information between the OTR M4 page at AliExpress and the User Manual, there is low voltage warning.
The question is: which levels should we follow? And does this really matter? :stuck_out_tongue:

User Manual:
5% (RED) > 3% (Blinking RED) > 0% (OFF)

–10% (RED) > –3% (Blinking RED) > –1% (OFF)

I haven’t measured the voltages at which the RED and the blinking RED start to warn. I will add information later on.

Concerning the charging process:
a) while charging the indicator led on the switch will be RED and when charged it will be BLUE

b) the flashlight can be used with the charging cable plugged in without the battery inside. In this case, the indicator LED will be BLUE. Turbo cannot be used in this “no battery” mode ( NOTE: I do not recommend this!!! )

According to the specs, charging would take 1 hour.

I didn’t test for the possibility to have “true” USB-C charging.


As mentioned above, the OTR M4 has a configurable UI, to some extent. This configuration is the what is called the “Gear Lock” in the user Manual and it similar to the OTR M3 Pro that I reviewed some years ago (https://budgetlightforum.com/t/-/54250).

Before stating the levels/modes I must mention that when placing the battery inside the flashlight and threading the tailcap in the indicator led in the switch will flash BLUE.

Advancing to the levels and modes, the OTR M4 has:
Ultra Low> Low > Medium > High + Turbo +Strobe / Beacon / SOS

NOTE: Strobe is called “POUNCE” in the user manual and OTR webpages

The flashlight has memory for the 4 regular levels (UL / L / M / H) and will turn ON in the last used level. The operation in the “regular” way is:


  • OFF >> press & hold for 0.5s = ON in the last used level
  • OFF >> double click = TURBO
  • OFF >> triple click = Strobe [ > Beacon > SOS > Strobe… (with single click between these)]
  • OFF >> press & hold 4s = light turns ON in the last used level > flashes 3 times > remains ON and locks level [“Gear Lock”]


  • ON >> single click = advances in levels UL > L > M > H > UL…
  • ON >> double click = TURBO
    > single click = last used level
    > triple click = Strobe
    > press & hold 0.5s = OFF
  • ON >> triple click = Strobe
    > single click = > Beacon > SOS > Strobe >…
    > double click = TURBO
    > press & hold 0.5s = OFF
  • ON (select a level) >> press & hold 4s = light turns OFF > flashes 3 times > locks the memorized level [“Gear Lock”]


The “Gear Lock” allows to lock 1 specific level that we want to use. When that specific level is locked, we are able to use the OTR M4 as a single level (ON / OFF) flashlight if we want to. Any of the 4 regular levels (UL / L / M / H) can be memorized to use the flashlight this way.
After choosing the level and locking it, the operation in the “Gear Lock” way is:


  • OFF >> single click = ON
  • OFF >> double click = TURBO
  • OFF >> triple click = Strobe [ > Beacon > SOS > Strobe… (with single click between these)]
  • OFF >> press & hold 4s = light turns ON > flashes 3 times > remains ON and unlocks level [“Gear UNLock”]


  • ON >> single click = OFF
  • ON >> double click = TURBO
    > single click = OFF
    > triple click = Strobe
  • ON >> triple click = Strobe
    > single click = > Beacon > SOS > Strobe >…
    > double click = TURBO
    > press & hold 0.5s = OFF
  • ON >> press & hold 4s = light turns OFF > flashes 3 times > unlocks the memorized mode [“Gear UNLock”]

NOTE: As with the M3 Pro, I found this “Gear Lock” very useful, specially when I want to use the ML level, or a Low/Medium level without having to remember what was the last used mode (memorized)! So I think this is an exceptional feature of this flashlight!


As there are different emitter options for this flashlight, there will be different outputs too.
OTR states on the User Manual, that the output tests were made with a 16340 battery and SST20 (6500K) LEDs, so it will change according to the LEDs used.

Still, these would be the outputs vs runtime:
ULTRA LOW = 6 lm >>> 3days
LOW = 180 lm >>> 2h15m
MEDIUM = 400 lm >>> 1h
HIGH = 880 lm >>> 35 m

TURBO = 1500 lm >>> s/d Nichia versions would produce 1200 lm SEE TEST BELOW


I did a 7 minute test to check the drop of Turbo. Test was done with the light at 1meter away from the lux meter. Please do not see this data as “scientific” and accurate, but as a demonstration.

Output started dropping after 30 seconds until 3m15s, more or less. Since then it stabilized.
The battery was at 4.17V in the beginning of the test and was at 3.87V after the 7 minutes test.

Time Lux
0m 2271
0m30 2261
1m 2055
2m 1565
3m 1018
3m30 995
4m 994
5m 994
6m 994
7m 993

I also did something like a “ceiling bounce” test, using the luxmeter configured to Lux.
I put 4 flashlights (1 at a time) near it, pointing it to the ceiling during some seconds. Here are the results. Again, please do not see this data as “scientific” and accurate, but as a demonstration.

Flashlight Lux
OTR M4 90
Olight S1R II 155
Acebam TK16 (lower Turbo) 91
RovyVon S3 80

Here we can see that the advertised max output of the OTR M4 is not near the max output if the S1R Baton II (claimed 1000 lumens). So I would say that the max output of the OTR M4 is also nowhere near the 1200 lumens…


Concerning the current pulled by each level, this is what we get (more or less):

Ultra Low > Low > Medium > High > Turbo

I should also mention that the parasitic drain of this light is 0.03mA / 37.5µA .


Time for some size comparison with other 16340 flashlights.
(in case you need more comparison with other lights, ask me)

OTR M3 Pro > RovyVon S3 > OTR M4 > Olight S1R Baton II > Acebeam TK16

OTR M4 > EagTac D25C


And now time for some beamshots :wink: That’s what a flashlight is made for: SHINE!!!

No PWM, as expected:

And how it looks like with that 4th emitter in the center :stuck_out_tongue:

As for the beam pattern, this is how it looks like.
It can be seen that there are some artifacts due to the optic (clear narrow) used. Also, the use of the 4th emitter produces a different shape when compared to other lights using the same Carclo 10507 and 3535 emitters.

I can also state that those “yellowish” shifts are due to the optic as wells, since with a 10511 or 10508 Carclo optic they do not exist. Using that type of optic would give even more flood and even less trow, however.

OF COURSE, these are only noticeable if we do “white wall hunting” or if we are indoor, since that outdoor, these artifacts are not “caught” so easily.

BTW, comparing another light using Carclo 10507 and the Osram W1 emitters, we see that there are really a lot of artifacts when using this optic. And I could show other examples, independently of the LEDs used.

OTR M4 vs Acebeam Tk16

And now some tint comparison :wink:
I really love the Nichia 5700K, which produce a neutral white beam, and reproduce colours as they are, specially “live” not in photo.

Vs RovyVon S3 (3 x Nichia 4500K-5000K / LEDiL SATU)

Vs Olight S1R Baton II (XM-L2 6500K / single TIR optic)

Vs FWAA (3 x Nichia 4000K / Triple TIR optic)

Vs Acebeam TK16 (3 x Osram W1 / Carclo 10507)

Vs EagTac (3 x Luxeon V2 4000K / Triple TIR Optic)

And some distance beamshots in outdoor use.

Dark > Light

To have a notion of how the OTR M4 looks like side by side with other lights, here go some comparisons:

OTR M4 vs S3 > S1R II > FWAA > TK16 > D25C

Vs RovyVon S3 (3 x Nichia 4500K-5000K / LEDiL SATU)

Vs Olight S1R Baton II (XM-L2 6500K / single TIR optic)

Vs FWAA (3 x Nichia 4000K / Triple TIR optic)

Vs Acebeam TK16 (3 x Osram W1 / Carclo 10507)

Vs EagTac (3 x Luxeon V2 4000K / Triple TIR Optic)


What I like:

- size and weight, since this is a compact flashlight, suitable for EDC

- overall construction, design, ergonomics, machining and finish

- configurable UI, specially the possibility to use the flashlight as single level light, and the possibility to lock each regular level (at a time)

- high CRI emitters, which is – for me and for many possible buyers – a big plus and that I think it was a smart from OTR to implement these type of LEDs in such a small flashlight

- USB-C charging, which is more and more convenient in mobility

- accessories, that have good quality and that are great to have, being a flashlight enthusiast or not, and that make this a good light to offer to someone less “savvy” on flashlights

- low parasitic drain, even if it is bigger than the RovyVon S3, but smaller than other E-switch lights


What I would improve:

- adding a glass lens (even if thin) above the Carlco optic, since it is prone to scratches and dust accumulation

- eventually opt for a 10511 optic to reduce the amount of artifacts in the beam

- find a way to prevent accidental activation in the pocket, specially when in the “Gear Lock”, that wouldn’t imply recurring to the pocket clip nor to lockout nor to press & hold. [I had an episode of accidental activation with the flashlight configured to have single mode, while it was being carried in the “coins pocket” of my jeans. Since then I am using the pocket clip to prevent that.]

- add a true Moonlight level, of 0.5 lumens or below

- have a possibility to disable memory, in order to always start in the lowest level

- although it is not “needed”, I would probably add the possibility to have a magnet, although I know it would make the flashlight longer (I can always glue one in the tailcap :stuck_out_tongue: )

- I believe that that lumens specs are not accurate, given the test did before, so I would like that OTR correct that information

Overall, despite some minor issues (claimed output, accidental activation – fixed) I am glad with this flashlight and I still think it can be a good option for an EDC light.

Here’s my video review:


If you have comments or questions leave it below!
Happy New Year BLF!! :beer:

Thanks for the comprehensive review and photos
Interesting design on the location of the centre LED

Thank you for another nice review, MascaratumB!

I am not sure if the central led is good for anything as it seems like most of the light coming from it is blocked by the optic. It would be cool as a second channel with a red led.

Great review :+1:
And a nice light

But I do not like 16340

In my opinion the worse choice in batteries

Better 18350

Regards Xandre

…And yesterday I was wondering why this brand / this light is not getting more press on BLF.

When I first got my hands on mine, I was amazed that they managed to squeeze 1000+ high-CRI lumens and type-C charging into such a tiny body, not to mention it also supports CR123A for emergency use. I’ve been using this to burn off all my half-used CR123s from my MF cameras, just for fun.

The beam artifacts are easily solvable with some D-C-Fix. At the cost of some throw, of course.

The lack of magnetic tail cap and lanyard hole is a real shame, though. For such an ultra-compact and floody light, magnets and lanyard can greatly enhance it’s real-world practicality.

About your “ceiling-bounce” test: Out of curiosity I tried to reproduce a round of similar tests with several lights I have at hand: single-LED reflectors, multi-LED TIRs, frost-filtered LEPs, etc.
What I found is the test result has a lot more to do with beam profile, candela, and distance to surrounding walls, than to do with lumens. Actually, I failed to draw a strictly linear correlation in any data sets. Too many variables at play here, as it seems.

I’m not denying the possibility that M4Turbo is less lumens than S1R. Actually from the tint comparison shot it might really be the case. However I do not feel a “ceiling bounce” test is reliable to demonstrate that.

Thanks akhyar :wink:
Yup, I guess it is the first time this “disposition” is used, being a quad but looking like a triple. I need to do some more testing with different optics to see if it makes a difference of having/not having it in terms of beam pattern and output/range.

Thanks Skylight :wink:
I guess the reply I posted above applies here as well :nerd_face:
Hum, you suggestion is very interesting! That would be great if they could implement something like that. The MCPCB would need to be different too, not only the driver, but maybe it could compensate for the lack of a true Moonlight level (at least in some occasions)!!

Thanks Xandre :wink:
I guess we will have our own preferences, and until some time ago I was also more focused on 18350s!
If on the one side the 18350 is much better (capacity, current), it is larger than 16340, that allows to have more compact flashlights! :sunglasses: I’m still hopping for the day that Lumintop puts out a 16340 version of the FW3A and of the EDC18 :innocent: Just for the sake of being more compact than the 18350 versions.

Thanks UNBLF :wink:
Hum, how does it work with the CR123a cells? I didn’t buy any to test the flashlight since they are more expensive here and hard to find. Still, you are right, having the possibility to use that cell in case there is no rechargeable option may be good.

Yes, the beam artifacts can also be solved by using DC-Fix, if one doesn’t have other suitable TIR optics. Also, maybe sanding the clear parts of the optic surface (not the dome over the LEDs) can make those shifts disappear. Maybe I can check it later.

As for the magnetic tailcap, that would have been a good add, right? Both that and a lanyard can be added through DIY, but it was only a matter of 2mm more in the tail and it would have been done.

Thanks for the input on the “not scientific and methodologically correct ceiling bounce test” :wink: As I explained I did it more for the sake of checking some relative output. However in reality (naked eye perception), the OTR M4 has less output than the S1R.
Even if it uses a floodier TIR and the beam is more “diffuse”, you can see in this photo that there is a big difference between them. I am not sure how the SST-20 behave, but at least with these Nichia LEDS, and a fully charged cell, they don’t seem near the 1200 lumens advertised for this light.

Still, for me it can still be a good EDC flashlight, specially using the “1 mode” option. How do you prefer to use it regarding this?

Thank you all :beer:

With CR123A the lumens and runtime are much more limited than 16340s. Only lower steps can be used. It’s more for emergency or unconventional uses. From what I hear Fire Departments use CR123A lights because the battery is much less likely to burn / explode in extreme high temp conditions. It should also be more tolerant (than non-cold batteries, I don’t know how they compare to Molicel “cold” line) to low temperatures so it could be a good back up for winter camping. I also tried to use 2xCR123A in 18650 lights from different brands and they generally work, given the light must accept “longer” 18650s since 2xCR123A is longer than unprotected 18650.

Thanks for the review!
If you have time could you check if unscrewing the tailcap with the light ON reduces the 5 minute Gear Lock reset wait time?
A single mode flashlight would certainly make up for no access to low from off. No fan of memory in flashlights, but a single level, user-configurable 16340 flashlight would be nice.
Thanks either way.

Thanks bansuri :wink:

Also, thanks for focusing this topic as I didn’t address it in the review text nor in the video.

So, I configured the light to have 1 level only. With the light ON, I unscrewed the tailcap. When screwing it back again, the BLUE indicator led on the switch flashed and when I tried to turn the light ON with single click, it didn’t let me, so it was reset to the “regular” use with 4 modes.

With the same 1 level configuration, with the light OFF, I unscrewed the tailcap, removed the battery, put it back in place again and screwed in the tailcap. It didn’t lose the single level configuration.

In conclusion, unscrewing tailcap with light ON resets to 4 levels, and unscrewing tailcap with light OFF for a short period (I’d need to check if those 5 minutes are accurate) doesn’t reset to 4 levels.

Again thanks for placing this question :+1: