Infinite Product Solutions 15mm Crush Washer Black Oxide. With a Black Oxide Finish this washer is made from durable steel and fits many M15 x 1 RH threaded barrels. Specifications for Infinite Product Solutions 15mm Crush Washer: Manufacturer: Infinite Product Solutions Gun Model: Heckler & Koch G3 Heckler & Koch HK33 Heckler & Koch HK93 PTR 91 Heckler & Koch HK91 Color: Black Fabric/Material: Steel Weight: 0.096 oz Gun Make: Heckler & Koch PTR Width: 0.82 in Length: 0.82 in Gun Type: Rifle Caliber: .308 Winchester 7.62x51mm NATO 5.56x45mm NATO Height: 0.15 in Finish: Oxide Features of Infinite Product Solutions 15mm Crush Washer Provides over 1 full rotation (360 degrees) for proper muzzle alignment Corrosion Resistant Package Contents: Infinite Product Solutions 15mm Crush Washer What firearm models does the manufacturer say Infinite Product Solutions 15mm Crush Washer is compatible with? The manufacturer suggests that Infinite Product Solutions 15mm Crush Washer is compatible with Heckler & Koch HK91 Heckler & Koch HK93 Heckler & Koch G3 Heckler & Koch HK33 PTR 91Infinite Product Solutions 15-CW-BS: 15mm Crush Washer Black Oxide