Haoge 64mm Screw Knob Clamp Adapter Mount for Quick Release QR Plate Camera Tripod Ballhead Monopod Ball Head Fit Arca Swiss The Haoge 64mm (2.52") Discal Clamp is a Arca Swiss compatible screw knob clamp. It has a captive knob, safety-stop grooves, and a hollowed-out design that reduces the weight of the clamp. You can use an screw to mount it to an AS style ball head or panoramic head, and it will accept any standard Arca-Swiss quick release plate. There is a 3/8" threaded hole at the center for mount the clamp onto a tripod or monopod, and also comes with a 3/8" to 1/4" screw adapter.