Convoy M21B Flashlight Review

Convoy has released the M21B flashlight, a single emitter thrower style light in 21700 format.  Read on for some testing!

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Official Specs and Features

Here’s a link to the banggood product page.

Versions

There’s only one body style of the M21B, but it’s available in 6500K and 5000K temperatures.  The 6500K is seen here.

Price and Coupon

This one is currently going for a reasonable $26.99.  That’s a referral link – clicking it won’t affect your price at all but will help me continue posting items like this one for review.

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Short Review

This is an inexpensive and well-made middle-range thrower, which benefits from the extra capacity provided by 21700 cells.

Long Review

The Big Table

Convoy M21B
Emitter:	Luminus SST-40 (6500K)
Price in USD at publication time:	$26.99
Cell:	1×21700
Turbo Runtime	High Runtime
LVP?	Flash Warning
Switch Type:	Mechanical
On-Board Charging?	No
Claimed Lumens (lm)	2300
Measured Lumens (at 30s)	1806 (78.5% of claim)^
Claimed Throw (m)	–
Candela (Calculated) in cd (at 30s)	1308lux @ 5.634m = 41518cd
Throw (Calculated) (m)	407.5^
All my Convoy reviews!

^ Measurement disclaimer:  Testing flashlights is my hobby. I use hobbyist-level equipment for testing, including some I made myself. Try not to get buried in the details of manufacturer specifications versus measurements recorded here; A certain amount of difference (say, 10 or 15%) is perfectly reasonable.

What’s Included

• Convoy M21B Flashlight
• Lanyard (already attached)

Package and Manual

Typical Convoy package.  Usually, these get to me quite beat up.  But the contents don’t show any wear.

There is no manual included.

Build Quality and Disassembly

Build quality is exactly on par with other Convoy lights.  No better, no worse.  Considering that it’s only $27, it’s exceptionally well built.

The knurling is perfect.

The head has acceptable cooling and mass for the 5A 100% output.

The cell tube removes quite easily and has big beefy square-cut thread on both ends.  The anodized threads mean that the light can be mechanically locked out easily (even past the lockout that the mechanical switch provides).  The cell tube is reversible, too.

Both head and tail end have springs.

And both springs already have the spring bypass.

The bezel unscrews easily, and the aluminum reflector comes out, too.

This reveals the emitter, which has a nice big centering ring.  Swapping the emitter should be a breeze.

Size and Comps

Officially: Diameter (Head/Body) 35.7 / 27.1mm
Length 141.5mm
Weight 120g

It’s a fairly good handling light.  It could have more mass in the head, and/or a larger reflector and not suffer, but it’s good as-is.

Here’s the test light with the venerable Convoy S2+.  Mine’s a custom “baked” edition Nichia 219b triple.  A very nice 18650 light.

And here’s the light beside my custom-engraved TorchLAB BOSS 35, an 18350 light.  I reviewed the aluminum version of that light in both 35 and 70 formats.

Retention and Carry

There’s really only the lanyard for retaining the light.  There are holes in the tailcap for attachment, and the lanyard ships already installed.

Actually it ships installed a little incorrectly since the better way would be to loop it through two holes instead of just one.  This would allow easier tailstanding.

There’s nothing else.  No pouch, and no pocket clip – it’s not really suited to clip carry though.

Power and Runtime

The primary power for the M21B is a single 21700.  With springs on both ends, any type 21700 should fit and work just fine.  The M21B will also work with other cells like 18650 or 20700, too.

You’ll likely want a fairly high-quality cell because the M21B draws around 5A on 100% output.  Here’s a runtime on 100%.  Basically, the light starts at 100% and then tracks down just a little before settling out at around 1550 lumens.  After that output falls as cell voltage falls.  There isn’t LVP, but the main (ie only) emitter flashes to alert to low voltage at around 3V.  This flash is noticeable and quite dramatic because at this point the output can still be as high as 700 lumens.  So a flash from 700 lumens to off for a second is quite noticeable.

Output on the next lower level (30%) is pleasantly well regulated for just over two hours, at which point the low voltage warning beings.

Modes and Currents

Mode	Mode Claimed Output (lm)	Claimed Runtime	Measured Lumens	Tailcap Amps
100%	100%		1806	4.94
30%	30%		738	1.52
3%	3%		78	0.17
0.1%	0.1%		~	0.03

Pulse Width Modulation

No PWM on any mode with this light.

Here you can see a “baseline” – a chart with almost no light hitting the sensor.

Then there’s the Ultrafire WF-602C flashlight, which has some of the worst PWM I’ve seen. It’s so bad that I used a post about it to explain PWM! Here are multiple timescales (10ms, 5ms, 2ms, 1ms, 0.5ms, 0.2ms) to make comparing this “worst” PWM light to the test light easier. That post also explains why I didn’t test the WF-602C at the usual 50us scale.

User Interface and Operation

The switch is a very Convoy switch:  mechanical tailswitch – a reverse clicky.  It’s a big switch with some texture for grip, a fairly low action, and very clicky.

Neither the Convoy official page nor the BangGood page describes the user interface of this light.  And with no manual, I’m kind of just free-wheeling it.  That said, it’s probably mostly like other single switch Convoys – the T2 for example.  This does not seem to be Biscotti.

Here’s a user interface table!

State	Action	Result
Off	Click	On (Mode Memory)
Off	Half Press	No Action
On	Half Press	Mode Advance (LMHT)
On	Click	Off

There does not seem to be any strobe (yay).  Also no shortcut to anything (boo).

LED and Beam

The emitter in my review copy is a 6500K Luminus SST-40.  Also available is a 5000K option.  The deep wide reflector is very smooth.

These beamshots always have the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure. These photos are taken at floor level, and the beam hits the ceiling around 9 feet away.

Tint vs BLF-348 (KillzoneFlashlights.com 219b version) (affiliate link)

I compare everything to the Killzone 219b BLF-348 because it’s inexpensive and has the best tint!

Random Comparisons and Competitive Options

Here’s a link to a relevantly filtered page on parametrek.com.  I use that site a lot!  There’s not much else comparing to the M21B at the moment.  Certainly, nothing in its price class!

Conclusion

What I like

• Build quality for low price
• Throw is respectable

What I don’t like

• No LVP
• Would be nice if the user interface was Biscotti, at least

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Notes

• This light was provided by BangGood for review. I was not paid to write this review.
• This content originally appeared at zeroair.org. Please visit there for the best experience!
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