Sunwayfoto DDC-60i Screw-Knob Clamp (60mm)
Description (from B&H): The DDC-60i Screw-Knob Clamp from Sunwayfoto is an aluminum Arca-type compatible clamp that fits most ball heads. It can be attached via the 3/8″-16 thread, or by using the included 1/4″-20 bushing adapter.
Two safety stop grooves on the clamp help prevent your camera from accidentally falling when the clamp is loosened for adjustments. A detachable bubble level on the clamp helps ensure that your camera is level to the horizon.