[Review] Sofirn SF31 (XM-L2, 1x18650)

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[Review] Sofirn SF31 (XM-L2, 1x18650)

Here’s a review for the Sofirn SF31.
The flashlight arrived inside a simple cardboard box.

Except from the flashlight, the package contains a lanyard, two spare o-rings, a microUSB cable,
a protected 18650 rated at 2800mAh and a regular microUSB charger.

The body of the light is anodized, while the pocket clip is highly polished.
As seen, the light’s dimension are pretty compact.
From the head’s bezel to the tailcap its length about 12.4cm.

The head of the light has a crenelated ring that works great in protecting the front glass.
The heatsink fins give the light a nice look and certainly help in dissipating the heat produced
by the higher output modes.

The tailcap switch is reverse clicky and is very tactile.
Thanks to the raised sides of the switch, the flashlight can tail stand.

The threads of both ends of the body are square cut and are fully anodized.

At 66gr, the light is pretty light.

Here’s a view of both springs used by the lights.
The spring on the tail side seems a bit thin but a tailcap bypass mod is always an option.
A brass retaining ring is used to keep both PCBs in place.

The bezel of the head can be unscrewed to give access to the LED star.
The light comes with an XM-L2 on a copper star while there is also a centering ring pre-installed.

After unscrewing the retaining ring, the tailcap comes apart quite easily.
The tail includes the rubber boot, a spacer and the switch itself

The switch looks like the one found in multiple budget priced flashlights.
It’s nothing fancy but it’s been proven to work.

Due to the centering ring used, the LED is nicely centered.
The light comes with an orange pill reflector which helps dissolve the artifacts that might be produced by such a small reflector.

User Interface

  • Turn on/off : Single press of the tailcap switch
  • Cycle through modes: Half press of the switch ( Moonlight – Low – Mid – High)
  • Strobe : Double half press while turned on

Current Draw Measurements

During my tests I used short DMM leads (18AWG) and a Samsung 25R 18650.

Mode – Current (A)
Moonlight – 0.02
Low – 0.07
Mid – 0.68
High – 3.01

When I was contacted by Sofirn for reviewing their light I made sure to take a look at their
Amazon store for more details about the product.
It seems that the light is listed as a 500 Lumen output, but as proven by the measurement, it’s capable of producing close double to what is it advertised.

I have tested this light’s driver in the past and it seems that it can push close to 4A with a proper
cell and a spring bypass.
It seems that I will be adding the spring mod to my todo list.


The light has a warm white LED installed.
I am not a fun of very warm tinted emitters but it is what it is Smile
The combination of the small, orange peel reflector with the largely sized XM-L2 emitter results
in a pretty big hotspot – great for indoor usage.

Control Shot





Batteries And Charger

The flashlight bundle includes an Sofirn branded 18650 battery and a simple charger.

The charge uses a regular micro USB power input.
According to its specifications, it outputs a maximum of 1A current.

The indicator LED blinks red while charging and green once the charge has been completed.
The termination voltage for charging has been set at 4.19V.

The battery has a reasonable amount of weight, 47gr.
In order to test its real capacity I used my Opus BT CT-3100 V2 charger.
After charging the battery to 4.19V, I discharged it at 500mA rate and got 2840 mAh of actual capacity.