Everything you need and everything you don't. Like you weren't going to buy your own grip and trigger guard anyway. This Nitrided lower parts kit is an outstanding LPK. Nitriding is a treatment to the metal, not a coating, so there's no added dimension to the major component parts. This means this LPK will fit more smoothly in your lower than a standard LPK. The major component parts are also post-Nitrided machined, so the trigger and hammer mating surfaces are extremely clean. Machining after Nitriding is extremely hard on the cutting tools, but Critical Capabilities rather sacrifice some tooling in order to squeeze everything they could out of this LPK.