Installed 4 for a buddy. Rough feeling to me. Didn't like the heavy buffer spring that comes with the kit, bolt moved back to battery so fast it skipped over the next round. Factory buffer spring, problem solved. Hope the shipping pin does not come out of the trigger mech, it's a bitch to put it all back together into a drop in type unit. I'm pretty sure I can double tap faster, and it would be much safer. Not a fan of the manipulation involved to switch to safe, if on binary, and choose not to fire the follow up. Like I said, rough, but entertaining nonetheless.