Fiesol Quick Release Plate QP-144750 which works with the Feisol Ball Head CB-50DC, and gives you the ability to rapidly swap items on the head. These are an Arca-Swiss style plate and should work with other Arca-Swiss clamps.
A quality product.
The Feisol Quick Release Plate is a simple, straight forward product that does its job for 3x less than the competitors QR Plate. I use mine to attach to a binocular harness to tripod head. Works well and a great value!