I've had two of these fail. I will first say that Streamlight is very helpful and good about replacements but there is one huge design flaw with these units. One side of the light is secured to the rail polymer/plastic and is an extension of the housing. If you bump this on anything, over-tighten it, god forbid- drop it... it WILL crack and fall off. The last thing I want to have to worry about on a self defense weapon is being careful not to bump the attached laser against anything if I ever actually needed it. And no, I did not over tighten them.
Pros: Features, easy to use.
Cons: Breaks very easily.
This review was written in the old system and had content requirements that are different than reviews written today.