The RAM-B-108B-A-366U consists of a v-shaped strap base, short double socket arm and 1" ball with 1/4"-20 threaded stell stud. The base accommodates rails from 1.0" to a maximum of 2.1" in diameter. To mount the 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 camera plate provides extra support and stability for cameras that rest on top of it. The male 1/4"-20 threaded steel stud will connect to any standard female thread found on camcorders and digital cameras.