The Sunwayfoto DDC-60 Screw Knob Clamp (60mm) is an all-metal Arca-style clamp that fits to just about any 3/8"-16 or 1/4"-20 threaded screw (a 1/4"-20 adapter bushing is included to convert the 3/8"-16 thread). Or attach it to many ball heads via the included slot screw. An integrated bubble level allows you to ensure that your camera's position hews to the horizon.
With a width of 2.08" and a length of 2.36", the DDY-64 fits many brands of ball heads, such as those from Arca-Swiss, Jobu, Really Right Stuff, and more. The clamp fits most Arca-style dovetail camera plates (plate and head not included).