Luth-AR A3 Upper Receiver Assembled Black. Luth-AR made these AR15 Upper Receivers from 7.7 oz. of durable lightweight 7075-T6 aluminum complete with a hard coat anodized finish so that it resists corrosion and wear. The Luth-AR A3 Upper Receiver Stripped is the best place to start when piecing together a customized firearm. The stripped version of the Luth-AR A3 Upper Receiver is great for a minimalist build since there are no rails to impede the placement of your sights scope or bipod. Specifications for Luth-AR A3 Upper Receiver Stripped: Manufacturer: Luth-AR Color: Black Finish: Hardcoat Anodized Caliber: 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Package Contents: Luth-AR A3 Upper Receiver Stripped What firearm models does the manufacturer say Luth-AR A3 Upper Receiver Stripped is compatible with? The manufacturer suggests that Luth-AR A3 Upper Receiver Stripped is compatible with AR-15Luth-AR FTT-EA1: A3 Upper Receiver Assembled Black