This universal shotgun cantilever vent rib scope mount fits most shotguns barrels with vent rib up to 3/8" Works with 12/20 gauge shotguns perfectly contoured to receiver. Vent rib cantilever mount is weaver/picatnny style and it is perfect for scope and red dot sights. This universal cantilever shotgun vent rib scope mount attach to vent rib shotgun barrel and provide an extra long weaver / picatnny style scope mount rail over the receiver. This Universal Cantilever Shotgun Scope Mount is perfect for quick barrel changes the scope is attached to the barrel and not the shotguns receiver. This rugged mount bolts onto rib shotgun barrels in minutes with no modifications to the shotgun gun. It Allows you to change barrels on your shotgun without losing the zero on your sighting system. Good for left-hand and right-hand shooters. Works with Weaver style rings. Mounting Hardware Included No Gunsmithing Required. Made From Aircraft Grade Aluminum. Color Black Length 11.313" Height 0.2".