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. Features All steel rings with a horizontally split design and only 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. Specs Part #: 721 Ring Height: Medium Fits Objective Size (Approx): 20-42mm objective Dimension A: 1" Dimension B: .400" Dimension C: .502" Weight: 3.2oz (pair)