The M21F is a general-purpose style flashlight, with moderately high output and reasonable throw, running on a single 21700 battery. Features a decent user interface and good current-controlled circuitry.

1. Introduction
2. Manufacturer Specifications
3. Package Details
4. Build
5. User Interface
6. Circuit Measures
7. Emitter Measures
8. Beamshots
9. Testing Results
10. Runtimes
11. Pros and Cons
12. Overall Rating
13. Preliminary Conclusions
14. Acknowledgement

Introduction

Upon my recent return to reviewing, the compact 1×21700 Convoy S21E was my first foray into budget models. That light was my first experience of this maker, which was very positive. So I decide to pick up their larger, budget thrower in this 1×21700 class, the M21F.

At the time when I ordered this sample, there was an option for the Luminus SFT40 or Osram CULNM1.TG emitters (both suitable for maximum throw), or the higher output Cree XHP70.2 – with all emitters available in a variety of colour temperatures. Although I expect the SFT40 and Osram emitters would do well in this build, I decided to go for the maximum output to see how it compares to other XHP70.2 lights.

I note this light is now available with the XHP70.3 HI emitter, which might be a good compromise to consider (i.e., greater throw and less chromatic variation for a little less overall output).

Anyway, let’s see how this XHP70.2 version performs in my testing.

Manufacturer Specifications

Note: as always, these are simply what the manufacturer provides – scroll down to see my actual testing results.

Feature	Specs
Maker	Convoy
Model	M21F
Emitter	XHP70.2
Tint	6500K
Max Output (Lumens)	4,000
Min Output (Lumens)	-
Max Runtime	-
Max Beam Intensity (cd)	-
Max Beam Distance (m)	-
Mode Levels	5 + Ramp
Flashing	Strobe
Battery	1x21700
Weight (w/o battery)	145 g
Weight (with battery)	210 g
Length	143.8 mm
Head Diameter	40 mm
Body Diameter	27.5 mm
Waterproof	IPX4

Package Details

Like the S21E, the M21F is shipped in a simple cheap cardboard box, wrapped in thin bubble wrap. Inside, you will find the following:

• Convoy S21E with a thin wrist lanyard, also attached
• If you buy the version with a battery included, a thin filter pad is included to block contact during shipping

And that’s it. There is no manual or instruction sheet, so you’ll need to check out reviews like this to learn how it works and what all the features are. Minimalist to be sure, in keeping with the price.

Build

From left to right: LiitoKala 21700 (5000mAh), Fenix ARB-L21-5000U 21700 (5000mAh), Sofirm IF25A, Fenix E35 v3, Convoy S21E, Imalent MS03, Armytek Wizard C2 Pro Max, Acebeam E70, Nitecore P20iX, Nitecore MH12SE, Lumintop D3, Convoy M21F.

The M21F is larger than its compact S21E cousin, a more “typical” size for a general purpose thrower light. It look more polished and substantial than the S21E.

The electronic switch is more refined here, with a small button with rubberized grip with an integrated clear ring (that shows charging status), along with a stylish blue bezel ring. Button feel is good, with a defined click. There are dim couloured LEDs under the switch which can produce a red, orange or green colour during charging. A more sophisticated implementation than the S21E build for sure (but see below, for my charging experience).

There is a small raised post on the positive contact terminal in the head, so flat top cells can easily be used. Tailcap is flat with a standard spring and retaining ring. Note that like my first S21E sample, the silver-coloured spring included here is fairly stiff, and resulted in some denting of the positive terminal of the battery. I know these springs were replaced with softer gold-coloured ones on later S21E editions.

There is an integrated USB-C charging port on the head of the light, across from the switch, under an attached rubber cover. Cover fits well enough to make me think the light is fairly water-resistant.

The light doesn’t have knurling per se, but rather a series of deep cut-outs with concentric circle “reeling.” I found grip to be pretty good on this model, as the reeling is deeper and more aggressive – better than on the thinner S21E body. The larger head, with cut-out fins, also helps with grip. Wrist lanyard is pretty cheap, and introduces a slight tailstand wobble the way it is attached be default – I recommend you re-thread it to the side cutouts on the tailcap (which is presumably why they are there, to prevent interference with tailstanding).

The light has a distinctive gun-metal blue annodizing, in a satin finish. Anodizing looks to be decent quality, although there are a few small chips on some of the raised reeling rings on the body tube on my sample (making me thing this is indeed type II annodizing, as is common on budget lights). Tailcap screw threads are square-cut and anodized, so you can lock out the light by a twist of the tailcap. Screw threads on the head are not anodized (and don’t need to be).

Any regular-sized 21700 cell (without an integrated USB-C charger) should fit and work in the light. You are best sticking with flat-top cells though, as longer cells (i.e., with a button top) would likely be too tight given the strong tail spring.

A solid build with good hand feel, it certainly feels like a higher-end budget build.

The XHP70.2 version here comes with a heavily textured reflector (I believe the SFT40 version comes with a smooth reflector). Reflector is quite deep, which should provide good throw.

The mineral glass lens has a light greenish AR coating, which I prefer. Bezel is stainless steel with crenelations. Not overly aggressive, but I’m sure it would hurt if you were hit with it.

I’m not doing white wall beamshots any more, but I did notice a rather yellowish corona around the hotspot, progressing well into the mid-spillbeam range on my sample. You see it even in the simple desktop shot above. In practice though, it is really only noticeable on a white wall though. This is a common occurrence with XHP70.2 emitters.

User Interface

The M21F has the exact same user interface that I described on the S21E. It has a choice of two distinct multiple-output mode sets you can select: one with a smooth ramp in output from min to max, and one with four discrete steps (1%, 10%, 40%, 100%/Turbo) plus a 0.2%/Moonlight level. Also available is a “Tactical” mode which only has the Turbo level. A strobe mode is also available, along with some other bonus features.

From OFF:

• Press-and-hold: Moonlight
• Single-click: Turns on to the memorized brightness level
• Double-click: Turbo
• Triple-click: Strobe
• 4 clicks: set to Tactical mode (i.e., only momentary 100% brightness)
• 5 clicks: Voltage check. The light will blink out the voltage to one decimal place, first by the main volt, then by the decimal point (e.g., 3 blinks, a pause, and five more blinks would mean 3.5V).
• 6 clicks: Switch between ramping mode and stepped mode
• 10 clicks: Electronic lock out. Click for another 10 times to re-activate the light. Note that I suggest you simply lock the light out by a twist of the tailcap instead.

From ON:

• Press-and-hold (in Ramping mode set): Ramp up to 100%/Turbo. Press-and-hold again to ramp down to 0.2%/Moonlight. Release at any time to select the desired level. Note that when you restart the ramp after selecting a level, it reverses direction on the next press and hold.
• Press-and-hold (in Stepped mode set): Step up to next level (4 main levels on the sequence, Moonlight is not on the main sequence). Press-and-hold again to step down in levels.
• Single-click: Off
• Double-click: Turbo
• 3 clicks: Strobe
• 5 clicks: Voltage check
• 6 clicks: Switch between ramping mode and stepped mode

Shortcuts:

• To Moonlight: Press-and-hold from off
• To Turbo: Double-click from any mode except Tactical
• To Strobe: Triple-click from any mode except Tactical

Mode memory:

Yes. The M21F will memorize any brightness level except for Moonlight and Strobe.

Low voltage warning:

Yes. The light will drop down to ~1% output and the switch surround will blink red before eventually shutting off at ~3V. Note that it can run for a very long time at this level before shutting down.

Reviewer Comments:

As before, I find this to be a very decent and versatile interface – easy to use, but with a decent number of options. Hand the light to someone, and it wouldn’t take them long to get used to it, the modes make a lot of sense. Switching between ramping and stepped mode sets is a bit peculiar with the six clicks, but it’s not something you will want to switch between often anyway.

Note that the Turbo mode steps down automatically after a period of time (scroll down for runtimes). And while I’m glad to see the extra ultra-low mode here, it is not actually low enough to be what I would consider a true Moonlight (see Testing Results for more info).

Circuit Measures

Pulse-Width Modulation (PWM):

There is no sign of PWM at any level – the light appears to be current-controlled. However, I did detect a faint oscillating noise pattern on two of the discrete levels, 10% and 40%, but not on the 1% or Turbo levels.

Step 40%

Step 10%

Step 1%

The frequency was 1 kHz on the 10/40% levels, and this is not visible in actual use. I am simply including the scope readings for completeness.

Strobe:

Strobe

Strobe frequency is a fast 10.1 Hz, the same as the S21E.

Charging:

The M21F has a single high-current charging rate of ~2.1A.

I normally like a two-stage charging feature (i.e., with a lower charging rate for when cells are heavily discharged). But the M21F’s output drops down to a super low mode when the battery is running low, and big red button flashes incessantly, warning you to shut down. In fact, it is actually very hard to get the cell below ~3.0V in this light . As such, this is reasonable compromise to stick with a single high charging rate integrated charger.

There was an issue with the charging feature on my sample. The charger would never go green, even with >12 hours plugged in. It progressed from red to orange as the battery charged, but the cell would always max out at ~4.12V, according to my voltmeter. It seems the integrated charger won’t go any higher on my sample. I tried other batteries, and the effect was the same – the charger terminates at ~4.12V, leaving the battery not quite fully charged (and the charging LED showing charge still in progress). I suspect this is just a quirk of my one sample

Standby / Parasitic Drain:

I measured the standby current at a negligible 39.5 uA on my sample.

This is nice and ultra-low standby current, and is not a concern for draining the cells. However, I always suggest you lock the light out when not in use to prevent accidental activation (and cut the negligible standby drain in this case). A single twist of the tail will lock out this light, thanks to the anodized screw threads.

Emitter Measures

This section is a new feature of my reviews, where I directly measure key emitter characteristics in terms of colour temperature, tint, and colour rendition. Please see my Emitter Measures page to learn more about what these terms mean, and how I am measuring them.

As explained on that page, since I am using an inexpensive uncalibrated device, you can only make relative comparisons across my reviews (i.e., don’t take these numbers as absolutely accurate values, but as relatively consistent across lights in my testing).

The key measures above are the colour temperature of ~6725K, and the very slight positive tint shift (+0.0036 Duv) to green at this temperature.

For CRI (Ra), I measured a combined score of 76.

These values are consistent with a cool white XHP70.2 emitter, and match my visual experience of this light.

Beamshots

All outdoor beamshots are taken on my Canon PowerShot S5 IS at f/2.7, 0.5 secs exposure, ISO 400, daylight white balance. The bend in the road is approximately 40 meters (~45 yards) from the camera. Learn more about my outdoor beamshots here (scroll down for the floody light position used in this review).

Click on any thumbnail image below to open a full size image in a new window. You can then easily compare beams by switching between tabs.

The beam pattern is good, with a nice mix of throw and spill (and the mild colour distortion around the hotspot is not noticeable in actual use outdoors). I would be curious to see how far it throws with a smooth reflector and smaller emitter.

Testing Results

My summary tables are generally reported in a manner consistent with the ANSI FL-1 standard for flashlight testing. In addition to the links above, please see my output measures page for more background.

All my output numbers are based on my home-made lightbox setup. As explained on that methodology page, I have devised a method for converting my lightbox relative output values to estimated lumens. My Peak Intensity/Beam Distance are directly measured with a NIST-certified Extech EA31 lightmeter.

M21F Testing Results

Mode	Spec Lumens	Estimated Lumens @0sec	Estimated Lumens @30 secs	Beam Intensity @0sec	Beam Intensity @30secs	Beam Distance @30secs	PWM/Strobe Freq	Noise Freq	Charging Current <3V	Charging Current >3V	Parasitic Drain	Weight w/o Battery	Weight with Battery
Moon 0.2%	-	19	19	-	-	-	No	No	2.1 A	2.1 A	39.5 uA	150 g	219 g
1%	-	36	36	-	-	-	No	No	2.1 A	2.1 A	39.5 uA	150 g	219 g
10%	-	445	445	-	-	-	No	0.99 kHz	2.1 A	2.1 A	39.5 uA	150 g	219 g
40%	-	1,100	1,100	-	-	-	No	0.99 kHz	2.1 A	2.1 A	39.5 uA	150 g	219 g
Turbo 100%	4,000	3,100	3,000	20,200 cd	19,400 cd	279 m	No	No	2.1 A	2.1 A	39.5 uA	150 g	219 g
Strobe	-	-	-	-	-	-	10.0 Hz	10.0 Hz	2.1 A	2.1 A	39.5 uA	150 g	219 g

Max output is much lower than the claimed specs (which I expect are theoretical “emitter lumens” and not actual ANSI FL-1 output lumens). The lowest mode is closer to 0.5%, so there no “Moon” mode here, just a reasonable low.

The M21F is also the second heaviest light in my line-up above. The larger mass should help with managing heat dissipation.

To see full testing results for all modern lights in my testing, check out my Database page.

Runtimes

As always, my runtimes are done under a small cooling fan, for safety and consistency. To learn more about how to interpret runtime graphs, see my runtimes methodology page.

As you can see above, the M21F is very well regulated, with very flat output at all levels tested.

Overall efficiency is excellent, pretty much exactly on par with the much more expensive Acebeam E70 (which also uses the XHP70.2). Convoy is obviously sourcing excellent circuit components.

Here is a blow-up for the first few mins of runtime on Turbo, so you can see the step-down more clearly in comparison to the other lights:

It is a good implementation of a step-down feature on Turbo, with a nice steady ramp down to the intermediate ~1700 lumen level beginning after 4 mins on max. I suspect the larger thermal mass is helping here.

Pros and Cons

Pros	Cons
Excellent output/runtime efficiency and regulation, on par with much more expensive brands.	Even with the textured reflector, beam shows a lot of colour variation in the corona and mid-spillbeam with this XHP70.2 emitter.
Decent beam profile with this emitter. However, this build is probably best suited to a smaller die emitter for maximum throw (or the newer XHP70.3 HI option).	Charger on my sample never goes green, (always shows as charging). Max charged battery voltage is only ~4.12V.
Good hand feel, with decent grip and nice implementation of an electronic switch.	My sample came with a dented positive terminal on the battery, similar to my early S21E model (corrected on that series over time).
A very decent user interface, intuitive yet with a good number of options.	Lacks a Moonlight mode, and max output is well below stated specs (but still reasonable for the class).

Another minor issue I noted is the ramping speed is rather quick. But given how few lights actually give you a choice of a continuous ramp option, this is hardly a complaint!

Overall Rating

Preliminary Conclusions

The M21F shows all the best characteristics of the S21E, in a more substantial build. It definitely has a more “classy” look and feel, and I particularly like the implementation of electronic switch on this model. A pity that the charger on my sample seems to terminate early, but I suspect that is an odd quirk of this one sample.

Circuit performance – in terms of regulation pattern and output/runtime efficiency – is excellent, on par with more expensive current-controlled lights. As before, I find the discrete levels are not really well spaced – but you always have the ramping mode available instead. And again, “Moonlight 0.2%” is really just a low mode (but to be honest, I’m not really looking for Moonlight in a thrower build).

Also as before, there are some minor issues I noticed on my sample, in keeping with the budget price. None of these are deal-breakers for me, but it does mean the light tops out at 4 stars in my view. The larger thermal mass here is definitely helpful though, in terms of supporting greater output for as long as possible.

Although it was good to be able to gauge max output performance with the XHP70.2 emitter, I regret not having the chance test the throw of one of the smaller profile emitters, like the SFT40. Given that the compact 1×21700 lights typically do a great job serving as general purpose lights, most people probably want to go with maximum throw on this build – especially given that deep reflector. And so, given the new XHP70.3 HI option available now, I think that is a great option to consider in this build.

Certainly a lot of good choices to consider in this budget thrower build!

Acknowledgement

The M21F was personally purchased from the Convoy store on Aliexpress in the fall of 2022. At the time of review, this light retails for ~$40 USD (~$60 CDN) with a bundled battery (and depending on emitter chosen).