Everything you need for your custom build, and nothing you don't. Just the basics from KAK. Bolt catch kit Magazine catch kit Takedown pin, detent, & spring Pivot pin, detent, & spring Buffer retainer pin & spring Ambi Selector, detent, & spring Hammer & trigger pins Hammer, trigger, & disconnect spring De-grease ambi selector screw threads and apply blue loctite when assemblying, Tq selector screws to 5-7 in/lbs or hand-tight