Convoy M21B

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Convoy M21B specifications

Brand & Model	Convoy M21B
Flashlight category	General Purpose
LED	Cree XHP70.3 HI R9050
Max. output	N/A
Max. beam distance	N/A
Max. beam intensity	N/A
Battery config.	1*21700
Onboard charging	None
Main modes	12
Blinkies	Strobe, SOS, Bike Flasher
Waterproof	N/A
Review publication date	April 2024

Anyone who’s been in the flashlight hobby for more than a couple years has probably heard the name Convoy thrown around once or twice, or thrice. No, not the 1978 movie where Martin Penwald and his gang of truckers terrorize the southwest. Convoy represents one of the OG flashlight brands. Simon Mao, the genius behind the brand, has made it possible to pick up a very high-quality and high-output flashlight for cheap. A bunch of guys and gals got into flashlights after picking up an S2+ and doing a triple mod with a spacer from kriba-ru and a MTN-17DDM with guppy3drv.

Ah…memories.

Now factory lights are available with options previously found on modded lights, and Convoy has also evolved in that respect, taking the old hosts we know and love like the S2+ and C8, and breathing new life into them with modern drivers and LEDs. That said, today I’m looking at one such light from Convoy. The Convoy M21B is the 21700-size version of the OG M1, which has been available since about 2010. The M1 is an 18650 light smaller than a C8 and bigger than the S2+. For years it was only available with a simple 7135 based driver or a linear FET driver with 3 volt LEDs. The M21B has been given a significant upgrade of late to bring it current for today. I’m looking forward to this one since I love nostalgia.

What’s in the package

Simon doesn’t waste effort or resources on a fancy box, and that’s totally fine with me. It saves you (the consumer) from paying for packaging that makes the flashlight more expensive. Here’s what you get:

• Convoy M21B flashlight
• Lanyard

That’s it! The lanyard was installed from the factory and it’s a typical cheap one, but would give good service. You can pick these up with a battery as well from Convoy.

This is a general-purpose light and strikes the perfect balance of size vs output. Convoy got it right with this one and it’s clear why it’s a popular light. The tube is covered with grippy knurling for a super-sure grip and the tube fills the hand, and I really like handling this light.

For switching, all M1s have a rear reverse clicky switch. It’s a good one too, with positive, snappy clicks and nice feel, and it’s easy to reach in all grip positions. It doesn’t have a pocket clip, but that’s okay since it’s a little too big for EDC, but is fine for larger utility pockets. There’s good-sized lanyard holes in the tailcap ears, and it will tail stand. Any holster meant for a 21700 size light would be a nice fit for the M21B. 

Build quality for the M21B is excellent. Like all Conoy lights, you get a lot of flashlights for a little money. How little?

The test light, as configured, comes out to around $35 US with a battery, and that’s a steal. The only competitor to this light is the Wurkkos TS22 for around the same price (on sale), or the Acebeam P17 Defender, and that retails for over $80 US. All the parts fit together just fine with no gaps or wonky fit up and the edges are chamfered and smoothed as well. Simon doesn’t go to great lengths to advertise features, but I’m sure he uses good quality aluminum alloys, so this is probably milled from 6061. The machining is very tidy with no issues.

The M21B comes in a variety of colors, including clear, gray, black, green, brown/sand, and orange. The test light came in the sand color and I really like it. The anodizing isn’t advertised, but I’d imagine it’s some sort of type III HA hard anodizing, and it’s also well done. Convoy’s finishes are one of my favorites; a really grippy matte with good texture and grippiness. The light can be fully disassembled for maintenance or upgrades, which is great and a hallmark of this brand. It takes a 20 mm MCPCB and a 22 mm driver.

Every joint is o-ring sealed and no IP rating is given, but since there’s no charge port, I wouldn’t worry about dunking the M21B. The tube threads are rectangular cut and fully anodized with light lube. Out of the box, they were decently smooth, but could benefit from some lube, so I added some SuperLube and now they

re super smooth. You get a nice bouncy gold-plated spring for the tailcap, but the driver has a brass post.

For the warranty, none is implied, but you’re covered for DOA lights, factory defects, and the like. Simon will take really good care of you and make any issues right. Ask me how I know that!

The Convoy M21B comes with a wide variety of 3 volt or 6 volt LEDs as a pre-assembled light or a host. The test light came configured as requested with the Cree XHP70.3 HI LED. This LED is pretty new, but has made its rounds through the flashlight continuum into some fan favorites. It’s the 3rd gen of Cree’s 7070 size XHP quad die high output LED. This one’s domeless from the factory for increased intensity as well with the added benefit of a cleaner beam with less of the obtrusive angular tint shift. It runs on 6 volts in this configuration, so 2 dies in parallel, two in series (the 12 v version is 4S). It’s available in cool white tints, warm white tints, R70 and even high CRI R9050.

The test light was spec’d with the R9050 5700K version. This LED is paired with a light orange peel reflector to help smooth out any irregularities in the beam. The beam with the XHP70.3 HI is great and it’s probably the nicest XHP beam I’ve ever seen (the C8+ with this LED is nice too). You get good beam distance with a lot of diffuse side illumination and a somewhat bright hotspot. It’s about a perfect general purpose beam! It’s clean too, with minimal chromatic aberrations or tint-shifting; way better than the domed 70.2s. The lens is a dual AR coated hardened glass unit, and it’s secured with a crenulated aluminum bezel that should offer adequate protection to the lens.

Spectral measurements: 

I used the Opple Lightmaster Pro to measure the flashlight at 3 meters from the sensor. 

Mode:	CCT:	CRI Ra:	duv
Turbo	6305K	92.1	0.0008

Dimensions: 

Convoy M21B	Millimeters	Inches
Length	141 mm	5.5 in
Head diameter	36 mm	1.4 in
Body diameter	27 mm	1 in

Dimensions are rounded to the nearest millimeter and the nearest tenth of an Inch.

Weight: 

Convoy M21B	Weight in grams	Weight in oz
Without battery:	121 g	4.3 oz
With battery VapCell T50	192 g	6.8 oz

Weight is rounded to the nearest gram and tenth of an Oz.

Flashlight size comparison with its competition:

Group 1: Group 1 left to right: Fenix TK16 V2, Convoy M21B, Olight Warrior 3S Limited Edition Ti, Olight Seeker 4, Acebeam P17 Defender

Group 2 left to right: FireflyLite X1S, Convoy M21B, Acebeam E75, Convoy C8+, FireflyLite E07X Pro

Group 3 reflectors left to right: Fenix TK20R (Luminus SFT-70), Olight Seeker 4 (Cree XHP50.3 HI), Convoy M21B (Cree XHP70.3 HI), Acebeam P17 Defender (Cree XHP70.3 HI)

This is one area where Convoy has advanced. Just 4 years ago, the only drivers you could get from Convoy for smaller lights were either linear FET or AMC7135-based drivers, but no more because now Convoy features an entire lineup of boost and buck drivers for 3-volt, 6-volt, and even 12-volt LEDs. Basically, if you need a driver, Simon has one for you. The M21B with the XHP70.3 comes with a boost driver, good for 6 volts 5 amps or 30 watts.

The driver might be modern, but the UI isn’t. It’s the tried-and-true 12-mode group interface that basically emulates ToyKeeper’s Biscotti UI. This UI’s been around a while, and it works great with a reverse clicky switch. You get 12 mode groups with single output or multiple output modes ranging from 0.1% to 100%, strobe, SOS, bicycle flasher, and batt check. The light comes set to the #1 (default) mode group, which has 0.1%, 1%, 10%, 35%, 100%, Strobe, Bike Flasher, and batt check.

Available modes: 

• 0.1%, 1%, 10%, 20%, 35%, 50%, 100

Available blinky modes:

• Strobe, Bike Flasher, SOS, Battery Check

From OFF:

• Press and hold: N/A
• Single click: Turns on in last memorized brightness level (mode memory is active by default)

From ON:

• Fully click the switch: Turns off
• Tap the switch: Advances to next mode
• Long press switch (more than 1 second): Returns to the first mode in the group (only works with mode memory OFF)
• Tap switch 10+ times: Enters configuration mode for setting mode groups and toggling  mode memory on or off

Mode memory:

• Yes. Remembers the last used mode. Mode memory can be disabled.

Shortcuts:

• None

Low voltage warning/protection:

• The light will drop to a very low level when the batteries reach a certain low voltage (not specified in the manual), and the light will start blinking slowly until it shuts down around 2.9 volts under load.

Strobe/blinkies

•  Strobe, SOS, Bicycle Flasher

Lock-out mode: 

• None, but light can be mechanically locked out by unscrewing the tailcap ⅛ turn

PWM

• None visible

Additional/summary info on the UI: 

• Even though it’s not true Biscotti, Simon’s interpretation is on point. Biscotti predates Anduril and really has a lot of flexibility. It’s sort of overshadowed by Anduril these days, but I still like it and think it’s still relevant.

How to switch mode groups on Convoy M21B?

1. To switch between the mode groups, from off, half-press the switch a bunch of times (over 10), and when it no longer turns on, stop and wait for the ‘buzz.’
2. There’s two buzzers: The first is for the mode group selection, the second is for turning mode memory on or off.
3. To turn on/off mode memory, wait for the second buzz, then click the switch off.
4. To switch modes, during the first buzz, the light will blink out the number of the mode groups, from one to 12 (1 blink = group 1, 2 blinks = group 2, etc.).
5. To select the desired mode group, click the light off on that group number. It’s not really meant for forward switches though (ask me how I know that one). The mode spacing is good, and the .01% is pretty low with 100% being direct drive if FET driven.

The boost driver should be nicely regulated, and the firmware includes LVP and thermal regulation set to 55 C.

The M1 was a 18650 light, and the M21B is a 21700 size light (the ‘21’). The 21700 cell is pretty much the de-facto flashlight battery these days since it offers both very high ampacity or can be really high capacity. You can order the light with a battery from Convoy, and Simon sells some nice ones, including the Molicel P42A or 5000 mAh versions. The M21B digested a variety of batteries I had on hand; flat top, button tops, protected, but the longest protected cells with internal charging and button tops were a bit long to comfortably fit. There’s no onboard charging with the M21B or even the M1, which is fine, but you’ll need a separate li-ion charger, sold separately, but you can order one from Convoy.

Charge type	Fits	No fit	Charge time
None	Standard flat top and button top, protected flat and button top	75 mm long 21700s	N/A

Lumen measurements

How Lumens are Measured: Understanding ANSI FL1 Standards How Lumens are Measured: Understanding ANSI FL1 Standards: The ANSI FL1 standards specify that output in lumens should be measured 30 seconds after turning on, as this is the standardized time for measuring brightness according to the industry standard. This is why we focus on this part in our measurements. The ANSI FL1 standards require an ambient temperature of 22 ± 3°C. We record the ambient the ambient temperature to identify potential reasons for any observed discrepancies.

Lumens are measured in my 50 cm integrating sphere with a Digi-Sense 20250-00 data logging luxmeter. The sphere has been calibrated with a Convoy S2+ measured to 260 Lumens and the figures are within 10% of actual.

Mode	Amps at start	Specified	Turn on	30 sec.	10 min.
0.1%	17 mA	?	2.5	2.5	–
1%	69 mA	?	25	25	–
10%	640 mA	?	322	321	320
35%	2.34 A	?	996	996	972
100%	7.98 A	?	2485 lm	1931 lm	935 lm

Ambient temperature during testing:

• 19.5 °C 

Parasitic drain:

• N/A µA/mA (it’s a clicky switch)

The output on 100% at start isn’t very impressive for a 70.3, but the LED isn’t being driven particularly hard and this is the high CRI version, so some output deficit is to be expected. Still, almost 2500 Lumens isn’t bad. The other outputs are comparable also.

Convoy M21B Battery Life: Runtime graphs

How Runtimes are Measured: Understanding ANSI FL1 Standards About ANSI FL1 runtime standards: The runtime is measured until the light drops to 10% of its initial output (30 seconds after turning on). This does not mean that the flashlight is not usable anymore. The last column shows how long the light actually works till it shuts off. If there is a + symbol, it means that the test was stopped at that particular point, but the light was actually still running. This happens on certain occasions, with certain drivers, firmware, or batteries.

Lumens are measured in my 50 cm integrating sphere with a Digi-Sense 20250-00 data logging luxmeter. The sphere has been calibrated with a Convoy S2+ measured to 260 Lumens and the figures are within 10% of actual. I use a Digi-Sense 20250-92 data logging thermocouple for the temperature measurements. The probe is affixed to the head using kapton tape and uses the same 5 second sampling rate for logging. I tested 10%, 35%, and 100%  modes. I used a Samsung 50S 5000 mAh 21700 and the battery was fully charged before each test.

Mode	Specified	Runtime (ANSI FL1)	Time till shut off
10%	?	7h 45min	7h 45min
35%	?	1h 40min	6h 30min
100%	?	1h 32min	3h 44min

The runtimes look great and the driver shows really good regulation for all tested modes. The output on 100% drops pretty rapidly in the first 30 seconds, but you still get over 1700 Lumens for nearly 3 minutes before another drop to around 1000 Lumens for over an hour and a half. This is pretty decent and about average for a light like this. High exhibited the same behavior from startup, and 10% was the endurance winner, running at 300+ Lumens for over 7 hours.

The LVP hits when the cell reaches 3 volts, and drops to roughly 10% output while blinking every couple seconds. This continues for a long time before shutting off. Temps were managed very well! The tube was hand-friendly for over 20 minutes on 100% and 35% and never went over about 60 C.

I compared the M21B with some other similar lights. The closest competitors would be the Acebeam P17 and the ArmyTek Prime C2 Pro Magnet, and both of these have higher output to start, but similar sustained output (both these cost nearly triple what the M21B costs). Convoy’s own C8+ with the same LED and driver has nearly identical performance, which was surprising since it’s hamstrung by a smaller battery.

Peak beam intensity and beam distance measurements

About Peak beam intensity: Understanding ANSI FL1 Standards About peak beam intensity The calculated value of distance in meters at which the flashlight produces a light intensity of 0.25 lux. (0.25 lux is about the brightness of a full moon shining on an object). This means that the intensity has decreased so much, it becomes difficult to see darker objects, or objects that don’t reflect light. The columns ‘Meters’ and ‘Yards’ use rounded numbers.

Beam distances are measured using a Uni-T UT383S luxmeter measured indoors at 5 meters using a fully charged Samsung 50S battery. Measurements taken at 30 seconds. The light allowed to cool between the 35% and 100% tests.

Mode	Specified	Candela measured	Meters	Yards
0.1%	?	125	22	24
1%	?	300	35	38
10%	?	3325	115	126
35%	?	10,200	202	221
100%	?	20,125	284	310
100% at start	?	26,800	327	358

Ambient temperature:

•  19.8 °C 

The throw figures look good too, and this is plenty of reach for a compact tube light with a 35 mm head.

Camera settings and distance: Photos taken with a Canon EOS R100 with Canon RF-S 18-45 mm STM lens. For the 40 meter shots, the camera is set to 0.3s, F5 ISO1600 and 5000K WB. 

Beamshots of the following flashlights compared:

• Convoy M21B
• Convoy C8+ XHP70.3 HI R9050
• Generic C8 with XHP50.2
• ArmyTek Prime C2 Pro USB Magnet

Please note that the following beamshots are mainly intended to showcase the beam pattern and beam quality, rather than overall performance. These images are typically taken directly after activation, and in different seasons or weather conditions, and therefore do not fully represent its overall performance. For accurate performance metrics, such as output, beam distance, and runtimes, you need to look at the performance section of this review.

Disclaimer: This flashlight was sent to us for review at no cost by Convoy. We have not been paid to review, nor have we been holding back on problems or defects.