The Boring Stuff

Sofirn sent me this light in exchange for a honest review. Here is the official product page but it’s also available from Amazon at a small markup. Below are the official specs.

What comes in the box?

The box is small, minimally branded, and made of thin cardboard. There’s a small foam pad at the bottom, but the light came wrapped in a bubblewrap sleeve so it was sufficiently protected. The battery comes inside the light with a small black disc isolating it electrically for transport. Also in the box is a manual, basic but decent lanyard, spare o-rings, a USB A-to-C cable, pocket clip, and a little card warning you to remove the battery insulator. I do wish a small split keyring had been included. Overall the packaging feels just a bit flimsy. You can see in the photo that it’s starting to come apart a little bit on the front right side. As a result, the box came open inside the larger Amazon box during transit. Nothing was damaged, fortunately.

Size & Measurements

From left to right:
Sofirn C01S
Sofirn SC21
Thrunite Catapult Mini
Emisar D4V2
Skilhunt H04 RC
Noctigon KR1
Fireflies E07x Pro

Measurement	Measured (mm)
Bezel Diameter	22.5
Maximum Head Diameter	23.5
Length	73.3
Switch Diameter	6.5
Switch Proudness	1.2
Tail Groove Depth	2.6
Tail Groove Width	2.6
Tail Groove Diameter (outside)	17.7
Tail Groove Diameter (inside)	12.5
Body Tube Diameter (internal)	17.1
Body Tube Diameter (maximum)	21.9
Pocket Clip Space (for pants/hat material)	2.5
Pocket Clip Width	6
Pocket Clip Thickness	0.7
Pocket Cip Slot Width	4.2
Pocket Clip Slot Diameter	19.5
Driver Diameter	19
USB Port Width	11
USB Port Depth	2.5
USB Port Height	7.5
Cooling Fin Thickness	2

User Interface

This incudes what is quickly becoming Sofirn/Wurkkos’ standard e-switch UI and it’s pretty good, but it should have come with Anduril 2.

The actions are # of presses followed by a hold (H) or a release (C). So, “1C” is one click and release. “2H” is two clicks but you hold down the last one.

State	Action	Result
Off	1C	On
Off	1H	Moonlight (not memorized)
Off	4C	Lockout
Any	2C	Turbo (not memorized)
Any	3C	Strobe
On (except Turbo)	1C	Off
On	1H	Cycle Mode (low-med-high, memorized)
On	4C	Toggle Smooth or Stepped Ramp
On (Moonlight or Turbo)	1H	Low
Turbo	1C	Memorized Mode or Off*
Turbo	2C	Turbo
Strobe	1H	Cycle Mode (strobe-SOS-beacon, not memorized)
Strobe	1C	Memorized Mode or Off*
Lockout	1C	Double Blink
Lockout	1H	Momentary Moonlight
Lockout	4C	Unlock (to memorized mode)

* If you access Turbo or Strobe from on, then single click, they will return to the memorized mode. If you access Turbo or Strobe from off, then single click, they will turn off.

I’ve got two minor gripes. 1C from turbo should turn the light off, not turn it back to the last used mode. 2C should do that. When using the smooth ramp, it ramps way faster at the low end than it does at the high end which is a minor annoyance. Overall this UI is pretty well thought out and is one of the best available.

Regardless of how good the UI is, it should have just come with Anduril 2. Sofirn has already demonstrated they’re willing to use it on other lights. Anduril 2’s simple mode is no more complex than Sofirn’s UI. I can’t think of any reason why they wouldn’t use Anduril 2 here. An SC21 Pro version with Anduril 2 may be in the works which is good.

Modes, Brightness & Throw

Disclaimer: The lumen numbers in this section are only estimates. I don’t have the equipment to do lumen testing, so I’m assuming the official turbo output claim for this light is correct and I calculate all other lumen numbers relative to that. All measurements were taken using the Ceilingbounce app on my smartphone.

Level	Lumens (Estimated)	Candela	Throw (meters)
Turbo	1000	4500	134
High	422	1900	87
Medium	102	460	43
Low	16	70	18
Moonlight	too low to measure	too low to measure	too low to measure

I measured parasitic drain at 39 microamps.

Regulation

Disclaimer: The lumen numbers in this section are only estimates. I don’t have the equipment to do lumen testing, so I’m assuming the official turbo output claim for this light is correct and I calculate all other lumen numbers relative to that. All measurements were taken using the Ceilingbounce app on my smartphone.

Battery Voltage	Lumens (Estimated)
2.96	117
3.31	333
3.54	667
3.7	767
4.15	1000

Regulation on the SC21 isn’t amazing. Turbo output does decrease decrease as the battery drains, but that’s now most lights are though, so it’s not a huge deal.

Runtime

Disclaimer: The lumen numbers in this section are only estimates. I don’t have the equipment to do lumen testing, so I’m assuming the official turbo output claim for this light is correct and I calculate all other lumen numbers relative to that. All measurements were taken using the Ceilingbounce app on my smartphone.

Turbo: Turbo starts out at 1000lm and stays near there for over two minutes. By three minutes it has dropped to 250 lumens. It fluctuates between ~250 and ~400 lumens until the 53 minute mark. I suspect this fluctuation in temperature is a result of some not-very-granular thermal throttling. Next it drops to just over 100 lumens (medium mode). It stays there for a few minutes and right after the 1 hour mark it drops to about 15 lumens (low mode). There it stays until roughly the 80 minute mark when it starts to slowly dim. It continued to dim from there until I stopped the runtime test at about 9 hours. I never observed any LVP and I measured the cell at 2.44V when I stopped the test. After a few hours it recovered to 2.96V.

High: High starts out at about 400 lumens and stays there for 53 minutes. Then it drops to medium for six minutes, then low for fifteen minutes, and then starts the same slow decline I noticed in the Turbo runtime. I ended the test at 90 minutes and measured the cell voltage a 2.45V, so no LVP again. After a few hours it recovered to 2.94V, pretty much just like the Turbo test. It’s worth noting that the light did not get too hot to hold in high mode despite the lack of a stepdown. 400 lumens sustained brightness is pretty impressive for a tiny light like this, especially with a high CRI emitter. It never got too hot too hold on this mode either.

Medium: Medium mode is a perfectly flat ~100lm for four and a half hours. Then it dropped to low and I stopped the test to protect the battery. It was at 3.17V.

Emitter & Beam

SC21 comes with a Samsung LH351D in the 5000K 90CRI variety. It’s a 3535 3V emitter known for its high output and efficiency despite being high CRI. It sits inside a surprisingly deep orange peel reflector and is well centered. I was unable to get the bezel off to get a look inside despite using a tremendous amount of torque. I believe it’s glued on (boo).

The beam is on the floody side and has well defined hotspot and spill without the transitions being harsh. It’s a good general purpose EDC beam. There’s nothing particularly noteworthy about it, which is a good thing I suppose. For all the beamshots below, my camera settings were locked.

There’s a bit of tint shift but it’s not bad in person. The reflector was not a bad choice but this light feels like it should be using a TIR optic to me. Maybe that’s what will come in the rumored SC21 Pro.

From left to right:
Skilhunt H04 | RC LH351D 4000K
Sofirn SC21 | LH351D 5000K
Fireflies E07x Pro | SST20 4000K FA4
Emisar D4V2 | FET+1 Driver | SST20 4000K (bin unknown)
Convoy M1 | H17Fx Driver | SST20 4000K (bin unknown)

Moonlight mode on SC21 is satisfactory. It’s not amazingly dim but it’s not too bright either. My guess is it’s right around 1 lumen. The tint differences in the photo above are a bit exaggerated.

Design & Construction

The design of the SC21 is good overall. The only area I find lacking is the clip (more details in the “Carry & Ergonomics” section). It matches Sofirn’s design language from many of their other lights like the SC31 Pro, SP32, etc.

Build quality is excellent, as I’ve come to expect from Sofirn. The knurling is simple but well executed. Machining is all high quality with no sharp edges. The anodizing is perfectly even. The threads appear to be trapezoidal cut (not triangular cut) and they’re sufficiently lubed.

Switch

Sofirn used an indicating electronic switch on the side of SC21. It’s black with a clear window in the middle. Under that window are some LED’s that glow when charging or for 5 seconds after the light has been turned on. When using the light, green means at least 30% capacity is left, constant red means less than 30% capacity is left, and flashing red means the light needs to be recharged immediately. The lighting in the switch is nice and bright, so much so that it’s caught my eye while I’m using the light even when I’m not looking for it. That’s important because there’s no low voltage protection to prevent you from running down the battery too far.

The switch is tactile enough to feel when it’s been actuated, but it’s softer than most. Most e-switches have an audible click to them but this one is virtually silent. I have to hold it up to my ear to hear it. It would be cool to be able to turn the switch backlight on all the time. Hopefully that feature will come on the rumored SC21 Pro.

Carry & Ergonomics

SC21 is a tiny light, so it’s not the most hand-filling. I didn’t have any issues using it in-hand though. The switch is easy to find and use. It’s certainly not fatiguing to hold. It’s light enough that you can easily hold it in your mouth for some quick hands-free light. It’s exactly what I’d expect from a small side switch light.

Carrying the SC21 is a bit of a mixed bag. It’s very small, especially coming off several weeks of carrying the gigantic Fireflies E07x. This is a light where you can legitimately forget it’s in your pocket. I love the bezel down clip orientation as it carries super deep and my thumb is already on the switch when I pull the light from my pocket.

The other part of that mixed bag is the clip. It’s just difficult to get into my pocket. It’s shorter than average bidirectional clip, so there’s not very much springiness or ramp. On longer clips you can stretch them a lot further before they deform and the pressure of the clip is more consistent. With this clip, right out of the box it’s like it was holding against the flashlight body for dear life. I bent it out and that helped a bit.

There’s not really a ramp at the bezel end of the clip, just a rounded bit. That doesn’t slide over the pocket well so you have to sort of grab it and lift it up when putting the light in your pocket. That’s not normally a huge deal but the clip is so small it’s hard to get a grip on it. Again, bending the clip out helped a little bit.

The final clip issue is that the bidirectionality doesn’t work. It’s not long enough for bezel-up carry to be viable as half the light sticks out of your pocket. It also doesn’t have enough ramp or space in the clip to be attached to a hat for use as a headlamp on any of the hats I own. The brims are just too thick, and I’m afraid if I were able to get the clip onto one, it would bend the clip out permanently.

Simply including a clip that’s 50-75% longer would have solved all these issues except it would suddenly be landing right on the charge port cover. I hope that for the SC21 Pro Sofirn offsets the charging port to one side like on the Q8 Pro, elongates the clip, and adds a little bit of ramp to the front like Olight does on some of their clips like the one shown below. I will give the credit for ensuring the clip lands on a nice smooth section of the light. I don’t anticipate this clip will be eating any pockets any time soon and it doesn’t interfere with battery changes.

Sofirn also included a lanyard and a magnetic tailcap. The lanyard is basic but it does the job just fine. The attachment points on the tailcap are set up in such a way that tailstanding is possible with the lanyard attached. I would have prefered to have two holes rather than one hole and a cutout though. The magnet in the tail isn’t super strong, but it will hold the light up on a vertical surface. It appears to just be held in by the tailspring and that doesn’t seem too difficult to remove with some really long needlenose pliers. I don’t have any pliers that long though so I was unable to test that theory.

I would have liked for Sofirn to have included a small keyring with the light. Something that could fit through one of the lanyard holes, maybe 5/16″ in diameter, that would allow the light to be carried on a keychain. Assuming the magnet could be removed, and because of the good lockout mode that unlocks to on, this would make a great high powered keychain light.

Batteries & Charging

SC21 uses a 16340 li-ion cell. An 800mah, unprotected, button top cell is included and it works well. u/ozSillen on Reddit was able to test his sample’s battery and it measured in at closer to 700mah.

When swapping cells, the spring pressure is fairly strong and it can make it hard to get the threads started correctly. I believe there’s enough room to fit a protected cell if you wanted to.

I tested with a fresh CR123A but on turbo it stepped down to high almost instantly and then down to medium after about 5 seconds. So CR123A’s can work in a pinch but they’ll only get you medium mode. There’s no low voltage protection so theoretically you should be able to squeeze every last microamp of energy from a CR123A if you needed to.

Charging is facilitated by a USB-C port opposite the switch and covered by a rubber flap. It worked well with both A-to-C and C-to-C cables. However, the port is pretty small and I was unable to fit a couple of my cables in for charging. I included measurements in the Size & Measurements section if you have a particular cable you really like to use. Fortunately, Sofirn provides a satisfactory and A-to-C cable in the box. Charging stops at 4.15V.

I want to take a second to praise Sofirn for their excellent execution of a rubber port cover. These are notorious for being flimsy and coming open by accident, leading to water ingress, but Sofirn did a stellar job with this one (and all of theirs I’ve tried). The cover has a lip around the backside of it that fits into a groove all around the inside of the port. This lip and groove holds the cover on more securely than any other design I’ve seen. I have zero concerns about water ingress on this one. During my testing it never came undone by accident, despite the fact that I kept the clip right below it and my pocket would undoubtedly drag on the flap every time I removed the light from my pocket. Well done, Sofirn.

While charging, the lights in the indicating side switch will come on. Green means the light is fully charged (or the battery tube isn’t tightened all the way). Blinking red means the light is charging. Charging took one hour and ten minutes. If you ever accidentally leave the light on and it gets really dim, make sure to turn it off, leave it for a few hours, and then plug it into the slowest USB port you have just to be safe (most computer USB ports are slower charging that dedicated power bricks). There are photos of the charging indicator in the switch section.

It’s fully functional when plugged in, with or without a battery. The only difference is that turbo mode is limited to the same brightness as high mode if you don’t have the battery installed.

Competition

Here are some lights in the same class as the SC21 and how they compare.

The elephant in the room is the Olight S1 series, now up to the Baton 3. Baton 3 is remarkably similar to SC21. They have similar batteries, switch layouts, UI’s, sizes, clips, and use cases. The key differences are price (Olight is over twice as expensive), clip (Olight is better), emitter choice (SC21 is better), charging (Olight uses magnetic and has an optional charging case while Sofirn uses USB-C), driver (Olight uses an unequivocally superior driver with excellent efficiency and regulation), and LVP (Olight has it built into the cell, Sofirn doesn’t have it at all). SC21 should win, but the poor clip really knocks off some points for me, and the lack of LVP makes me hesitant to recommend it to non-enthusiasts. I think all things considered it’s a draw.

Thrunite T1: slightly larger, pricier, brighter, floodier, inferior UI, micro-usb recharging, larger battery capacity: better for muggles but worse for enthusiasts.

Wowtac W1 & Thrunite W1: lower price, wider head, inferior UI, micro-usb recharging, lower brightness, worse emitter, marginally better clip, protected battery, more body color options: better for muggles but worse for enthusiasts

Conclusion

Sofirn made a valiant effort here to de-throne the venerable Olight S1 series (now on the Baton 3). They nailed the size, build quality, emitter choice, and price point. The sub par clip and lack of LVP are significant drawbacks though. If they fix those things and add Anduril 2 in the SC21 Pro, I think it will be a home run. For the standard SC21 though, I think it’s best suited for enthusiasts who aren’t as picky about clips as I am. It’s good, but it’s not great like I was hoping it would be.

Thanks to Sofirn for sending me this light for review!