It works well apart from not having a switch on tail switch so the light just remains on. But If you made a short tube with switch I think folks would appreciate it.
Correct while the threads appear to be the same pitch, the Sofirn short tube I think are a little more square so you get a couple of turns then it gets tight, I didn’t want to force it and damage the threads. But…if you can deal with using the twist of a tail cap as an on/off switch it works really well performance is good. Another little trick too is the pocket clip on the FC-12 works well on the Sofirn SP31-PRO short tube setup. The original Sofirn clip only works well when using the full 18650 tube but with a little tweaking the FC12 clip can be made to fit well on the short tube SP31-p. I really like the FC12 as a light, I’m not a big fan of 2 switch lights, they kinda a bit annoying to use as you need to active 1 switch to turn it on then the other switch to configure the ramping or whatever funtion you want. The FC12 is just a bit too long IMO for an 18650 light. Like compared with say a warrior mini Olight or SR2 baton pro or SP31-PRO it’s roughly 30-40% longer. So an 18350 tube would be a great option to purchase separately or come with the light. I have the green Vapecel T-14 18350 cells which have 1400mAh capacity which is darn fine for such a small cell.