The RAM-B-108BU consists of a 1" diameter rubber ball connected at a right angle to a v-shaped base. The RAM-B-108BU accommodates rails from 1.0" to a maximum of 2.1" in diameter. To mount the RAM-B-108BU base, place the saddle shaped plate on the rail then wrap the metal clamp strap around the rail and plate. Tighten the screw knob on the metal strap with a screw driver until the strap has a firm hold on the rail. The RAM-B-108BU is an alternative mounting base for Beechcraft airplanes with a "throw over yoke".