11.5" Government profile Barrel Assy w/F marked FSB and 2 pc Handguard 1-7 Twist Starts with Luth-AR's 11.5a ^2 barrel with F Marked Front Sight Base, 5.56 barrel made from 4150 CMV with a 1-7a ^2 twist mated to their A3 Flattop receiver which includes the Luth-AR bolt carrier, charging handle, forward assist and ejection port cover. Upper Specs: 7075-T6 Forging Hard coat anodize Black Bolt Specs: Bolt: Carpenter 158 steel 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 Mfg: Luth-Ar