Luth-AR AR-15 .308 Ejection Port Cover Assembly for .308 Upper Receiver Black. 308 Ejection Port Assembly for .308 Upper receiver Specifications for Luth-AR AR-15 .308 Ejection Port Cover Assembly: Manufacturer: Luth-AR Color: Black Gun Model: AR-10 Caliber: .308 Winchester Package Contents: Luth-AR AR-15 .308 Ejection Port Cover Assembly Spring and port door pin What firearm models does the manufacturer say Luth-AR AR-15 .308 Ejection Port Cover Assembly is compatible with? The manufacturer says that Luth-AR AR-15 .308 Ejection Port Cover Assembly is compatible with AR-10Luth-AR 308-UR-05A: AR-15 .308 Ejection Port Cover Assembly for .308 Upper Receiver Black