Convoy L21B SFT40 Review – Best Budget Thrower?


Pricing & Availability

Reddit user katsincerity lent me this light for review. Here are the official product pages with a battery and without a battery where you can see current pricing.

What comes in the box?

The box is thin cardboard. It’s a bit sturdier than Convoy’s flimsy white boxes used for smaller lights, but not as sturdy as their nice two-piece boxes with foam used for their larger lights. It’s probably sufficient to protect the light in transit. The following items are included in the box:

  • The light itself
  • Lanyard (attached to the tailcap)
  • Battery (inside the light, optional)

Design & Construction

The design is very simple with a narrow body tube, a few small cooling fins, and a simple flared head. I think it looks great.

Build quality is great for the price point. The anodizing is expertly applied with a satin finish. There are no sharp edges or blemishes anywhere. The threads are smooth and lightly lubricated. The pattern is the same on both ends, but the head threads are longer and unanodized so the body tube isn’t reversible.

Size & Measurements

Lumintop FW3A | Fireflies E07x Pro | Convoy L21B SFT40 | Sofirn BLF LT1 | Wildtrail WT90

MeasurementMeasured (mm)
Bezel Diameter62.6
Maximum Head Diameter62.6
Switch Diameter16.0
Switch Proudness-2.0
Body Tube Diameter (internal) 21.9
Body Tube Diameter (maximum)26.0
Body Tube Diameter (mode)26.0
Body Tube Length75.6
Tailcap Diameter27.5
Tailcap Length31.5
Driver Diameter22
Included Battery Length70.4
Included Battery Diameter21.3
I did not take the head apart for measurements because the focus is perfect and the light does not belong to me.

Weight without battery: 219g
Weight with included battery: 285g

User Interface

The user interface is one of the better mechanical switch firmware’s, but it still lacks some features.

L21B uses a reverse clicky mechanical switch. A “click” is a full depression of the switch to the point that it clicks. A “tap” is a quick half-press and release without fully depressing to the point of clicking.

OnTapCycle to the next mode
On20+ TapsEnter programming mode

This light comes with Convoy’s “12-Group” firmware. It has a variety of modes organized into 12 mode-groups. You can choose any one of those 12 mode-groups and even enable/disable mode memory if you choose. Those are really nice features.

The two features I miss having are a double-tap Turbo shortcut, and an easily-accessible voltage readout. It would be great if Convoy added a 3rd programming option to the 12-Group UI that allowed the user to enable a double-tap Turbo shortcut. Then I could use one of the groups with lots of modes without it taking forever to access Turbo.

A “battery check” mode is included on some mode groups, but it doesn’t blink out voltage. It just blinks 1-5 times, which is a bit ambiguous. It’s also only on some mode groups (and not usually the ones I like). I’d love for a voltage readout to be included that’s accessible via 10 quick taps. That’s very unlikely to be activated by accident but it would be very useful and accessible from any mode group.

Emitter & Beam

L21B is available with a selection of emitters, but this particular sample has a Luminus SFT40. I think that’s the best option overall for this light. It’s brighter and more efficient than most throw-focused LED’s. Plus, it happens to include Convoy’s excellent 8A Buck driver. I did not disassemble the head for this review because this light does not belong to me and I did not want to mess up the perfect centering.

The beam is fairly narrow but still usable. The spill is relatively bright and can easily be used to see around you while illuminating something far away. The hotspot is perfectly focused with a crisp, defined edge. There’s some corona between the hotspot and spill but it’s clean with no flower petals. Overall it’s a very impressive beam.

Convoy L21B SFT40 | Wildtrail WT90
Convoy L21B SFT40 | Mateminco FW2
Convoy L21B SFT40 | Thrunite “Thrower” Headlamp

In the beamshots above, the trees where I’m aiming the hotspot are 175M away. In the beamshots below, the park bench where I’m aiming the hotspot is 42M away.

Convoy L21B SFT40 | Wildtrail WT90
Convoy L21B SFT40 | Mateminco FW2
Convoy L21B SFT40 | Thrunite “Thrower” Headlamp

Mode Chart

Disclaimer: All of my measurements are taken at turn-on. Lumen measurements were taken on a Texas Ace 3.5″ Lumen Tube. A candela measurement was taken at 10 meters with an Opple Light Master III on the highest brightness, and other candela figures were calculated relative to that. CRI, CCT, & DUV data was taken for each mode from a few feet away at the center of the hotspot with the Opple Light Master and Waveform DUV Calculator. Runtime tests were performed with the Ceilingbounce app on my smartphone. All of these tests were performed with a fully charged optionally included battery unless otherwise specified. I cannot measure moonlight directly, so moonlight readings are calculated based on the brightness relative to the next-lowest mode. None of this is professional equipment, so take all of these measurements with a grain of salt.

Above are the official specs, followed by my own measurements below.

LevelLumensCandelaThrow (Meters)CRI (Ra)Color Temp. (K)DUV (Tint)
The hotspot was too bright on the highest two modes for me to get Opple readings.

Mode Spacing: depends on the mode group you choose. Some are well-spaced, some are not. The default mode group spacing is fairly good, but the “0.1%” mode is not as dim as I would like (1 lumen or less).


Performance: is great. 100% lasts nearly four minutes before thermal stepdown begins. It settles down to the same as 35% mode.

Thermal regulation: is present but doesn’t work very well. It’s a known issue on Convoy lights that they have thermal regulation but only between 100% and 35% mode. If a Convoy light thermal throttles it will only drop down as low as 35% mode but not further. That means that under the wrong circumstances they can overheat.

LVP: is present and works well. There’s a low voltage warning in the form of the main emitter blinking. There’s also a low voltage shutoff that happens then the battery is practically empty. You can re-activate the light after low voltage shutoff in an emergency but it will shut itself off again after a short time.

Driver & Regulation

If you choose the SFT40 emitter option in L21B it will come with Convoy’s excellent 22mm 8A Buck driver. It’s more powerful, better regulated, and more efficient than most of Convoy’s drivers.

Regulation is above average. 100% mode is affected by cell voltage but output is still respectable until the cell gets fairly low. 35% is only affected then the cell is near empty, and even then it’s only a small drop in output. Other modes are perfectly regulated. This is great performance at this price point.

Note: All regulation measurements are taken at turn-on so they do not reflect any thermal or low voltage stepdowns that may occur. A value of 0 indicates low voltage shutoff immediately upon activation.

PWM: No PWM is visible to my eyes or camera, nor audible to my ears.

Parasitic Drain: L21B uses a mechanical tailswitch that completely disconnects the circuit when it’s turned off, so there is no parasitic drain.


The switch is a reverse clicky and is located on the tail. It’s covered by a standard Convoy 16mm rubber boot. I usually prefer forward clicky switches and I wish Convoy offered that as an option on the product page. A forward clicky is fairly easy to swap in here by disassembling the tailcap with snap-ring pliers, de-soldering the reverse clicky, soldering on a forward clicky, cutting the nub off the inside of the switch boot, and reassembling. There are some alternate drop-in switch options available too: metal lighted reverse clicky, rubber lighted reverse clicky, remote switch.

Carry & Ergonomics

Ergonomics are fine. Reverse and cigar grips both work well. A forward grip works fine too but you have to break grip to access the button. The body texturing provides some grip, but it isn’t very aggressive so it may be a little slippery in wet conditions.

The only carry method included is a basic lanyard. It should also fit fine in a Convoy L6 Holster.

Tailstand: works fine and is fairly stable.

The user who lent me this light for review was interested in getting a pistol grip for it, like those old-school pistol grip spotlights. I designed & 3D printed one that uses the optional remote switch. The STL is available here if you want to print one yourself.

Batteries & Charging

If you so choose, you can get L21B bundled with a LiitoKala Lii-50E, which is a fine cell for this purpose. Any unprotected 21700 cell with an 8A discharge rating will work nicely. I tried a protected 21700 cell but it was too long to fit. A protected 18650 would work fine in a pinch.

No charging solution is included and 21700 cells with charging built in will not fit. If you must have built in charging, an 18650 with a charging port should fit but you will sacrifice some runtime.


Here are some lights in the same class and how they compare.

Noctigon K1: Similar size & weight, more emitter options (including the same SFT40), integrated charging, much fancier UI, backlit side switch, 3-5x the price.

Acebeam L19 2.0: similar size, heavier, fewer emitter options (including the same SFT40), cool dual-switch UI with instant turbo, TIR instead of reflector, optional remote switch, more durable

This section is not comprehensive. If I didn’t include a particular light here, it doesn’t mean it’s bad or doesn’t deserve to be here. I simply cannot list every possible competitor.


L21B SFT40 is a no-frills thrower at a great price point. This is about as much throw as you can get without the light getting comically large or the beam getting comically narrow. I highly recommend it.

Thanks to Reddit user katsincerity for lending me this light for review!

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