This is the curved adapter which suits narrower type stocks or those with a curved bottom. As a general rule, if the underside of your stock is as curved as a golf ball you need the curved adapter. The adapter is mounted in place of the sling stud and includes a wood screw and 5M screw to suit most stocks. The adapter has a built in sling stud. The adapter has a dense foam pad to protect your stock. This adapter is made from 7075-T7351 Aluminium. This aluminium is used in the aerospace industry as it's one of the highest strength aluminium alloys available. Spartan Precision Equipment Curved Rifle Adapter Plate SP02-040