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 kit comes with short arm, 1" ball 1/4-20 thread, 33-57mm hose clamp, 19-44mm hose clamp and rubber sleave optimal for mounting the SmartyCam HD Camera system or other devises.