Luth-AR 18 in MARK12 Complete Upper Barrel Assembly MLOK Black 18. The barrel is made of 4140 Chrome Molly providing accuracy and durability. The 1-9 twist rate is optimized for stabilizing heavy projectiles. This assembly includes a Picatinny rail for mounting optics and accessories. Easy to install and use. Designed for serious shooters this assembly is built to provide exceptional performance and reliability. Starts with our 18 in 5.56 Mark12 barrel made from 4140 Chrome Molly with a 1-9 in twist mated to our A3 Flattop receiver which includes our bolt carrier charging handle forward assist and ejection port cover. The upper is then topped off with our lo-profile gas system and our ergonomic 15 in Palm Handguard with KeyMod or M-LOK slots and a Picatinny top-rail. Specifications for Luth-AR 18 in MARK12 Complete Upper Barrel Assembly MLOK: Manufacturer: Luth-AR Caliber: .223 Remington Barrel Length: 18 in Color: Black Gun Rail: M-LOK Magazine Included: No Package Contents: Luth-AR 18 in MARK12 Complete Upper Barrel Assembly MLOK Luth-AR BAA3-M12M: 18 in MARK12 Complete Upper Barrel Assembly MLOK Black 18