Easily adapts to securely fit rails from 7/8 diameter to 1-1/4 diameter, round or square. Made from engineered nylon resin, the Stealth Universal Mount features a clamping block that can be rotated 90 degrees into the round or square positions. Multiple size notches seat to your specific railing. Four fasteners apply strong clamping force. Elastomer center block prevents rotation and damage to your boat.