Aluminum Alloy 20mm to 11mm Weaver Rail Mount Adapter for Airsoft - Black Quick detachable design with easy cam locking lever for fast installation and detachment Rotatable sling stud built in is perfect for mounting bipods or attaching to sling swivels Works great with Harris bipods or any other bipods that mount onto standard sling stud Fits all Standard 20 mm Picatinny Rail.