The mirror ring has the function of height adjustment and quick removal. It is suitable for 21mm standard Picatini rails and 30mm and 1-inch rifles. The rifle frame is made of aircraft grade 6061 aluminum alloy and has been processed by precision CNC (tolerance:+/-0.01 mm) to ensure accuracy and durability. Details: Model: Picatinny/dovetail rifle mirror ring, height adjustable Net weight (1 set): 90g Center height: 32 mm to 38 mm (1.26 inches to 1.5 inches)/36 mm to 42 mm (1.42 inches to 1.65 inches) black Pipe joint: 25.4mm/30mm (1 inch/1.18 inch) Guide rail matching: 11mm/20mm standard Picatinny guide rail, 11mm dovetail guide rail Material: 6061 aircraft grade aluminum alloy Package contains: 2x adjustable height rifle mounts 2x rings 25.4mm 2x wrench