Installed on an FNH FNS-9 9mm rail under the barrel. Instructions minimal, but easy to install. Initially, adjusting to keep a small piece on board failed until I figured out how to put it just so. Warning about not turning adjustment screw more than 2 turns buried, so screw is now buried and unit is useless. Never able to align with 3-dot sights. Bright, easy to turn on/off. Doesn't weigh down the barrel or get in the way of trigger finger. Would like it if I could figure out how to align it.
Pros: Bright, easy to use
Cons: Easy to mess up, never aligned with gun
This review was written in the old system and had content requirements that are different than reviews written today.