The Acratech Quick Release Clamp is a quick release adapter that accepts any of the "Arca" style plates, available from Acratech and from Arca-Swiss, Kirk, Wimberly, Really Right Stuff, Foba, etc. It mounts onto a 3/8" screw and features a "double-speed" rubber quick release knob that opens and closes twice as fast as standard "Arca" style clamps.