I had it in a 300 BLK lower, and swapped it to a AR9 lower for PCC testing. Technically it's a 2 stage trigger, but when you shoot USPSA matches, you pull the trigger so quickly that you're using it as a single stage trigger. It's adjustable from 2.5 to 5 lbs. The AR9 would double fire with the trigger set at 2.5 lbs so I bumped it up to 3 pounds and I've had no further problems with it.