This is a .22 long rifle conversion kit for any ar 15 that converts it to fire .22 long rifle shells. An excellent way to practice shooting your ar 15 without having to fire expensive .223 or 5.56 rounds through it. Simple installation you just take out your bolt carrier group and drop this one in and your ready to go it uses your same barrel you don’t have to change out anything except using the .22 long rifle mags that come with it too. This is the stainless steel version, with the added ition of being able to use your forward assist on it. I’ve used it for a while and it was fun and didn’t have any malfunctions.