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 degree and used on wider or narrower dovetails for the best fit.Features : Asymmetrical reversible side clamp fits a 3/8? or 11mm dovetail ,Uses Torx style T-15 socket cap screws, 25 in/lb. of torque recommended.,