Spike's Tactical set out to offer the best factory lower parts kit on the market! The lower parts kit they came up with exceeds military specifications by a long shot, they also have a much better fit, and finish! 100% made in the U.S.A. with a lifetime warranty.Kit includes: Rounded hammer and hammer spring (works with all calibers). Trigger and trigger spring. Disconnector and disconnector spring. Stainless steel hammer and trigger pins with black oxide finish. Safety selector. Safety selector detent. Safety selector spring. Bolt catch. Bolt catch plunger. Bolt catch roll pin. Bolt catch spring. Magazine catch. Billet magazine catch button. Magazine catch spring. Pivot pin. Takedown pin. Takedown/pivot pin springs and detents. Aluminum trigger guard w/spring loaded detent. Trigger guard roll pin. Buffer retainer spring. Buffer retaining pin. Spike's Pro Grip. 1/4x28 Allen grip screw. Star lock washer for grip screw.