Features: 8-40 adaptable (Mark 4)-Mark 4 tactical bases are the only bases to accommodate both the oversized 8-40 screw and a 6-48 screw, providing compatibility with the widest range of modern tactical firearms Dual Dovetail bases accept all Leupold rotary dovetail rings All Leupold optics offer performance that makes them equally at home in hunting or tactical environments, thanks to their outstanding accuracy, legendary ruggedness, and absolute waterproof integrity Leupold's trademarked Dual Dovetail system provides a classic low-profile mount for scopes on a variety of popular actions