Sofirn SC21 Flashlight Review

Sofirn SC21 Flashlight Review

A new light like the Sofirn SC21 flashlight is a bit unusual. It’s a 16340 light! Add an indicating e-switch, a magnet, and more… Read on!

Official Specs and Features

Here’s a link to the Sofirn SC21 flashlight product page.


There is just one version of the Sofirn SC21 flashlight.  It’s available as a kit, too though.


Without the cell (“SC21 Alone”) the package is $20.99.  With the cell (“SC21+Battery”) the package is $23.99.  If you make a purchase, I recommend grabbing the kit – the cell is worth the extra $3.  This light is available on Sofirn’s newly revamped website!

Short Review of the Sofirn SC21 Flashlight

For $21, the Sofirn SC21 flashlight is extremely hard to beat.  The size is great – despite nearly everyone forgetting about 16340 cells, they still make for great EDC flashlights.  Aside from size, this is a feature-packed light.  Indicating e-switch, tailcap magnet, USB-C charging, and a nice reflector….  There are a couple of things I don’t care for so much, though.

Long Review

The Big Table

Sofirn SC21 Flashlight
Emitter: Samsung LH351d (5000K, 90CRI)
Price in USD at publication time: $23.99
Cell: 1×16340
Turbo Runtime Graph High Runtime Graph
LVP? Questionable
Switch Type: E-Switch
Quiescent Current (mA): 0.11
On-Board Charging? Yes
Charge Port Type: USB-C
Charge Graph
Power off Charge Port “with cell: all modes
without cell: all modes except Turbo”
Claimed Lumens (lm) 1000
Measured Lumens (at 30s) 769 (76.9% of claim)^
Candela per Lumen 5.8
Claimed Throw (m) 135
Candela (Calculated) in cd (at 30s) 236lux @ 4.504m = 4787cd
Throw (Calculated) (m) 138.4 (102.5% of claim)^
Claimed CCT 5000
Measured CCT Range (K) 4700-5000 Kelvin
Item provided for review by: Sofirn
All my Sofirn reviews!

^ Measurement disclaimer:  I am an amateur flashlight reviewer.  I don’t have $10,000 or even $1,000 worth of testing equipment.  I test output and such in PVC tubes!!  Please consider claims within 10% of what I measure to be perfectly reasonable (accurate, even).

What’s Included

Sofirn SC21 flashlight what's included

  • Sofirn SC21 flashlight
  • Sofirn 800mAh 16340 (standard button top)
  • Spare o-rings (2)
  • Charge cable (USB to USB-C)
  • Lanyard
  • Pocket clip
  • Manual

Sofirn SC21 Flashlight Package and Manual

Sofirn SC21 flashlight warning

The manual is a booklet.  But I disassembled it, scanned it, and broke down the pages just because of how much I <3 you all. Below is the full English manual.

Build Quality and Disassembly

Sofirn SC21 flashlight feature photo

First of all, let us not forget that this light is offered at $21.  That’s a ridiculously low-cost light, especially for what all is on offer here.

Now there is a thing or two I don’t love about the build, but at $21, and being that it’s just personal preference, it’s very easy to overlook those.  I don’t love the knurling.  It’s very good knurling!  It’s just … something.  Sort of mismatched with the rest of the light design – I’m not sure we even need to see knurling on this light at all.  Very minor point though!

Here’s the tailcap, which has a little bump out to house the magnet.  The edge is also even with this bump out, and allows room for the lanyard holes.

Sofirn SC21 flashlight tailcap

Cooling fins in the head are minimal, but that’s ok.  The light is drawing around 2.5A on turbo.

Sofirn SC21 flashlight cooling fins

Here you can see that the bezel is smooth.  It looks removable, but I was unable to remove it.  I can’t say if this is because of threadlock or what.

Sofirn SC21 flashlight bezel

The head comes off the body easily, over smooth anodized threads.  Because of this anodization, it’s possible to mechanically lock the light out with a very light loosening of the head.  I recommend this, as quiescent current is fairly high here.

Sofirn SC21 flashlight head off

Only the tail ens sports a spring; the head has just a brass button.  I did not explore the option, but the spring looks to be removable, so you could remove the magnet if you wish.

Sofirn SC21 flashlight tail spring and head button

Size and Comps

Length: 73mm
Body Diameter: 22.5 mm
Weight: 39g (Not including pocket clip or battery)

If the flashlight will headstand, I’ll show it here (usually the third photo).  If the flashlight will tailstand, I’ll show that here, too (usually the fourth photo).

Sofirn SC21 flashlight in hand

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.

Sofirn SC21 flashlight beside torchlab boss 35

Here are a few other random lights I had laying around!  Hanko Trident Full Twist in brass, Sofirn SC21, Torchlab BOSS 35, Okluma DC1 in aluminum.  I haven’t reviewed this specific Okluma – maybe I should?

Sofirn SC21 flashlight with Hanko Torchlab and Okluma

Retention and Carry

A friction fit pocket clip is included, but not installed by default.

This clip fits only on the tail end of the light but is a two-way clip.  I have historically not loved two-way clips and this is no exception, but the execution here is fairly good.  There’s a tradeoff being made though.  The clip is short, which means it doesn’t get in the way of head removal.  (This is good – the clip doesn’t scratch the head when twisting.)  But the clip is short, so while using this on a cap will work, the Sofirn SC21 flashlight will protrude by almost half of its body length over the front of the bill. Pick your poison?

Sofirn SC21 flashlight pocket clip hug

Also included on the Sofirn SC21 flashlight is a couple of lanyard hole attachment points.  These are interesting because they feature a gap to allow tailstanding while the lanyard is installed.

Sofirn SC21 flashlight lanyard holes

Sofirn SC21 flashlight lanyard holes

Sofirn SC21 flashlight lanyard holes

The idea here is great, but in reality, the implementation is less so – just give me two holes for the lanyard to go through, as a Convoy S2+ has, and let’s call it good.  Or maybe there’s some other explanation for this setup that I don’t yet know?

Sofirn SC21 flashlight lanyard in use

The tailcap magnet is easily strong enough to hold the Sofirn SC21 flashlight.

Sofirn SC21 flashlight tailcap magnet

Power and Runtime

The Sofirn SC21 flashlight is powered by a single lithium-ion cell – in this case, a 16340.  An appropriate cell is included – an 800mAh button top.

Sofirn SC21 flashlight included 16340

Sofirn SC21 flashlight included 16340 Sofirn SC21 flashlight included 16340

The cell is installed into the light in the usual way – positive end toward the head.

Sofirn SC21 flashlight included 16340 installed

Runtimes follow.  Turbo steps down fairly quickly, but not in such a way that it seems to be gaming the ANSI standard.  In fact, Turbo drifts downward as cell voltage declines, and then finally steps down (likely) in response to the temperature created.  Funny, after mentioning it in a recent review, we see the output modulate back up after the flashlight reaches an acceptably low temperature.

Sofirn SC21 flashlight runtime graph

The next to levels of output show very flat output until the stepdowns.

Sofirn SC21 flashlight runtime graph

Sofirn SC21 flashlight runtime graph

Notably, on the test for Medium, I did not observe low voltage protection.  The product page says “voltage detection, low power remind” but doesn’t state lvp.  So I won’t say it’s a problem because Sofirn seems clear about it.  But I’d much rather the light shut off at 2.7 or 2.8V or so… There’s no need for a light like this to not have lvp.


On-board charging is available and happens via this USB-C port in the head.  A press-in cover protects the charge port.

Sofirn includes a quite nice USB to USB-C cable.

Sofirn SC21 flashlight charge cable

I tested the charge cycle with both USB to USB-C and C to C.  The charge looks about the same for either, but it’s good to know that C to C works just fine.

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo 1000 1h 769 2.54
High 400 1h 308 0.67
Medium 100 4h 84 0.16
Low 10 18h 13 0.03
Moon 1 85h 0.7 6.26mA

Pulse Width Modulation

Weirdly, one mode seems to have PWM.  I’m not able to see it though, so it seems acceptably fast.

For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor.  Also, here’s the light with the worst PWM I could find.  I’m adding multiple timescales, so it’ll be easier to compare to the test light.  Unfortunately, the PWM on this light is so bad that it doesn’t even work with my normal scale, with is 50 microseconds (50us).  10ms5ms2ms1ms0.5ms0.2ms.  In a display faster than 0.2ms or so, the on/off cycle is more than one screen, so it’d just (very incorrectly) look like a flat line.  I wrote more about this Ultrafire WF-602C flashlight and explained a little about PWM too.

User Interface and Operation

The Sofirn SC21 flashlight is controlled by a single switch.  It’s an e-switch on the side of the head.

Sofirn SC21 flashlight e-switch

This switch also has indicating features – below it’s seen indicating red for low voltage.  Notably, the switch will indicate for 5 seconds after the light is turned on, as follows:

Green: remaining battery power is good
Red: remaining battery power is poor (less than 30%)
Red Flashing: recharge or swap cell immediately.

Sofirn SC21 flashlight e-switch

There’s a surprising amount of travel on this switch.  It’s also quite proud.

Sofirn SC21 flashlight e-switch backlit

Here’s a UI table!  Note that this user interface is just like the Sofirn SP35, which I reviewed previously.

State Action Result
Off Click On (Mode Memory)
Off Hold Moonlight
On Hold Group 1: Mode cycle (Eco, Low, Medium, High only)
Group 2: Ramp up
Any (except Turbo) Double Click Turbo
Turbo or Strobe Click Previous state
On Click Off
Turbo Double Click Moonlight
On Click 4x Switch between Group 1 and Group 2
Any Click 3x Strobe
Strobe Double Click Strobe advance (Strobe, Beacon, SOS)
Off Click 4x Lockout
Lockout Click 4x Unlock
Lockout Click Main emitter blink 2x to indicate lockout
Lockout Hold Momentary Moonlight

Why you’d want to double click from Turbo to get to Moonlight, I have no idea.

Group 2 (Ramping) is very similar to the above Group 1, except holding the switch will cause the light to ramp up.  Loosening then holding the switch again within 1.5s will cause the ramp to switch directions.  So it’s possible to ramp up or down.  Double click still gets Turbo.

LED and Beam

One of the main important features of the Sofirn SC21 flashlight is that it features a Samsung LH351d emitter.  This is a 5000K temperature, and I applaud the great choice here by Sofirn.

Sofirn SC21 flashlight emitter

Sofirn didn’t go for “short” on the SC21 and used a nice deep reflector.  This gives a great beam profile.

Sofirn SC21 flashlight reflector

The bezel is flat with no shape, so light does not escape when headstanding.

Sofirn SC21 flashlight in use

Also, see here that the switch is indicating in green.

Sofirn SC21 flashlight in use


LED Color Report (CRI and CCT)

The readings on this SC21 show a CCT of 4700K to around 5000K and CRI above 90.  Both of these are good.


These beamshots are always with the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure.

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

I keep the test flashlight on the left, and the BLF-348 reference flashlight on the right.

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


What I like about the Sofirn SC21 Flashlight

  • Good to see a new 16340 flashlight available!
  • User interface offers something for most users (ie ramping is there if you want it)
  • Switch is easy to find
  • Indicator on switch is very clear and clean
  • Complete package is a very good and low cost
  • USB-C charging (and also C to C charging works!)
  • Good choice of 5000K emitter

What I don’t like about the Sofirn SC21 Flashlight

  • Does not seem to have low voltage protection
  • Two-way pocket clip


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