Starts with the Luth-AR 16a ^2 Lo-Drag, Classic Bull Barrel, made from 4150 CMV with a 1-7a ^2 twist mated to their Lo-Drag flattop receiver which includes the Luth-AR bolt carrier and charging handle. The Free Float version features the Lo-Drag Palm handguard which includes the Luth-AR bolt carrier and charging handle. Upper Specs: 6061-T6 Extruded material Hard coat anodize Black Bolt Specs: Bolt: Carpenter 158 Extractor: 4140 Alloy steel Army Spec Heat Treatment Manganese Phosphate Bolt Carrier Specs: Carrier: 8620 steel Cam pin: 4340 Alloy steel Carrier key: 4130 Alloy steel Army Spec Heat Treatme Mfg: Luth-Ar