Spike's Tactical Gen 2, Semi-Automatic, Billet Lower Receiver, 223 Rem/556NATO, Black Finish, Includes All Small Parts Except Fire Control Group STLB200 This lower receiver design was engineered to shave weight and increase strength. Now you can have a billet lower receiver with full ambi controls close to the weight of a standard forged receiver without sacrificing any strength. All edges and surfaces have been 3D chamfered to reduce snagging.