As a police officer, I need my gear to work right the first time every time. Unfortunately, while at the range, the M3 would pop off the rails of my Glock 23 after firing only a few shots. And go with an LED light rather than the halogen. Once soot gets on the lens of the light, it greatly reduces the brightness of the light. I ended up replacing my M3 with a TLR1 and have had no problems since.
Pros: Inexpensive
Cons: Pops off when firing
This review was written in the old system and had content requirements that are different than reviews written today.