From amateur gun builder to seasoned expert gunsmith; this complete lower receiver parts kit is for you! San Tan Tactical's AR-15 lower receiver parts kit is a great addition to your AR-15 build. This 17-piece kit includes the following: bolt catch, bolt catch plunge, bolt catch spring, bolt catch roll pin, mag release, mag release button, mag release spring, buffer retainer spring, safety, buffer retainer, buffer detent spring, safety detent, trigger guard, trigger guard roll pin, takedown detent springs, takedown detents, takedown pins. All Parts meet or exceed Mil-Spec. Note: Fire control group and grip are NOT INCLUDED.