75mm Half Ball. Step one: Identify the problem. You need to mount a flat-mount fluid head or sliders to a 75mm bowl tripod. Step two: Rent this. This isn’t really science!

3/8-Inch Stud. The 3/8-inch stud is compatible with most flat-mount heads.

Compatibility. Like its name says, this is for use with a 75mm bowl tripod. If you need a half-ball adapter for a 100mm bowl tripod, you’ll want the Kessler 100mm Ball Kit.