I just received the ACR Firefly PRO SOLAS Strobe from one of the on-line retailers. First impression is that it is well built and has a battery compartment very similar to the Streamlight Sidewinder. Although the two lights are similar in size they are very different lights.

The switch on the ACR Firefly requires a very long movement that should preclude it accidentally activating. Also when it shipped the piece of hook & loop/velcro was wrapped such that the switch cannot move. That may be a clue as to how a user should pack the light.

After inserting the batteries (NiMH), I found the light activates: 1) Strobe, then 2) Steady, then 3) SOS and if you turn the light off after mode 2 (steady) and turn it on a good while later it activates with mode 3 -- it doesn't reset to restart at mode 1.

I would prefer that it reset and always started as a steady light, then strobe, then SOS. But I'm sure they had their reasons.

YMMV. No affiliation other than as a customer.