KAK Industry provides just the essentials for your custom build. Everything you need and nothing you don't. Reliable and durable bolt catch kit Durable and reliable magazine catch kit Takedown pin, detent and spring for secure and reliable assembly of your firearm Pivot pin, detent and spring for secure and smooth firearm assembly Buffer retainer pin and spring for secure buffer retention and reliable operation Ambi selector, detent and spring for versatile and reliable firearm control Hammer and trigger pins for secure and reliable fire control group assembly Hammer, trigger and disconnect spring for reliable and consistent fire control operation De-grease ambi selector screw threads and apply blue Loctite during assembly for secure fastening, torque selector screws to 5-7 in-lb or tighten by hand to ensure proper installation and prevent loosening during use