The Rimfire rings are designed to fit a very wide selection of rifles with either a 3/8?” or 11mm dovetail. This is made possible by using a solid asymmetrical reversible clamp that can be flipped 180° and used on wider or narrower dovetails for the best fit. – All steel rings with a horizontally split design and only ½” wide. – Assymetrical reversible side clamp fits a 3/8 or 11mm dovetail. – Securely mounts to firearm with Torx style T-15 socket cap screws 25 in/lb. of torque recommended.