The CMMG Gunbuilder Kit is a customizable lower parts kits for the AR-15 platform. This kit provides all the minor, mil-spec parts generally used in an AR-15 build, while still allowing the flexibilty to add common aftermarket upgrades, such as a pistol grip and match grade trigger components. Customizable lower parts kits offer an economical way to get all the small pieces needed for an AR-15 lower, without wasting money on the parts you won't use!Kit IncludesBolt CatchBolt Catch PlungerBolt Catch Roll PinBolt Catch SpringBuffer RetainerBuffer Retainer SpringHammer PinMagazine CatchMagazine Catch ButtonMagazine Catch SpringPivot PinPivot Pin Detent Pivot Pin Detent SpringSelectorSelector DetentSelector Detent SpringTakedown PinTakedown Pin DetentTakedown Pin Detent SpringTrigger PinDoes NOT IncludePistol GripPistol Grip Screw and WasherTrigger or HammerTrigger and Hammer SpringsDisconnectDisconnect SpringTrigger Guard or Roll Pin