The ProMediaGear C60 Arca-Swiss Type Quick Release Clamp, is useful for adapting QR plates to tripod heads, stands, or supporting devices. Unique steel bushing inside the center of the clamp adapts with either 1/4"-20 or 3/8"-16 threads. The 1/4"-20 comes standard. Since the bushing is steel its also much more durable than aluminum and the threads will not get stripped. Additionally the bushing can be removed and the clamp can be top mounted to tripod heads utilizing an M6 countersunk screw. Tightening or Loosening the clamp locking knob attaches or releases the Arca-Type plate. With center finder mark and laser etched scale precise positioning can be achieved. Top of the line materials like T6061 aluminum and stainless steel have been used and all parts are CNC precision machined, for solid yet lightweight construction, the clamp is smooth and very pleasant to use. The steel bushing to convert to 3/8"-16 thread is separately available. If you wish to convert your ball head to Arca-Type tripod heads a anti-twist pins A16 are available separately.