I bought this for my Gen 4 G21, which Crimson Trace said it would not fit. After taking some measurments, it look like I could make it work. The only dimension that was different was the distance from the front of the trigger guard to the face of the grip. On my Gen 4 G21 was 2mm shorter. I was a little scared at first to take a dremel to my new $115 light. I did and with some careful grinding it fits perfectly.
Pros: Very bright for a small package. Instant on pressure switch
This review was written in the old system and had content requirements that are different than reviews written today.