The Sons of Liberty Gun Works AR-15 lower parts kit comes with almost everything you need to finish building your lower receiver. Also known as the blaster starter kit, the only components missing are the grip and trigger group. Every component in this kit is made to exceed Mil-Spec to ensure ultimate reliability in your AR. The SOLGW bolt catch and spring are cast from AISI 8620 per USGI TDP while the KNS Precision Machine safety and takedown pivot detents are made from hardened stainless steel. Even the magazine release is made from steel as opposed to the commonly used aluminum.