RAM Yoke Clamp Base with 1″ Rubber Ball and 1/4-20″ Tap for Camera or VideoThe RAM-B-121BAU, yoke clamp mount with 1/4″-20 thread, will fit rails from 0.625″ to 1.25″ in diameter. The 1″ rubber ball is set at a right angle to the plane of the mount, so when connected to a rail, the ball sits parallel to the rail. Material: Powder Coated Marine Grade Aluminum Ball Size: 1″ Rubber Ball “B” Size Note: The “U” in the part number reflects product packaged in poly bag.