Luth-AR 308 A3 Upper Receiver Black. 308 A3 Stripped Upper Receiver is machined from 6061-T6 aluminum extrusion for excellent strength and features black hard coat anodized finish for wear resistance. Specifications for Luth-AR .308 A3 Upper Receiver: Manufacturer: Luth-AR Color: Black Finish: Hardcoat Anodized Black Fabric/Material: 7075-T6 Forging Caliber: .308 Winchester Gun Make: AR Platform Gun Model: AR-10 Condition: New Projectile Caliber: .308 Caliber Weight: 17.2 oz Features of Luth-AR .308 A3 Upper Receiver 1913 Picatinny Rail .151 low height DPMS (Gen1) A3 low height Package Contents: Luth-AR .308 A3 Upper Receiver What firearm models does the manufacturer say Luth-AR .308 A3 Upper Receiver is compatible with? The manufacturer says that Luth-AR .308 A3 Upper Receiver is compatible with AR-10Luth-AR 308-FTT-EA: 308 A3 Upper Receiver Black