Gun Nuts Match Fire Control Group Lower Parts Kit - The Schmid Tool Gun Nuts line of AR-15 Parts was crafted by Schmid Tools, a company that has been producing fire control groups and lower parts kits for military contracts since 1980. Schmid Tool knows exactly what goes into making every part perfect. Trigger Hammer Disconnect Hammer Spring Trigger Spring Disconnect Spring Hammer Pin Trigger Pin Color: Nickel Trigger Type: Single Stage Pin Size: Small (.154in)