This steel castings has round cross section. Use the narrow swivel at the front of your triggerguard, on a boss-head screw behind the guard, or through the rib. Swivel is 5/16" wide inside dimension at the mounts. Includes a 6-40 mounting screw. Swivel will accept a sling up to 1-1/4" wide. This casting will need to have the casting gate removed.