This is a knob with a large washer which reaches up through the Mitchell plate for about 1" extra on the dolly and into the ball adapter to catch hold of the head bolt. and now available in a shorter reach of about 1/2" in 3/8-16 and 10mm

Adapt your ball bottom pan head to Mitchell top plate for dollies, cranes, leveling heads, etc. Available to fit ball heads from 75 mm to 150 mm including models for Sachtler, Cartoni, Vinten aO'Connor. Ask for others. These adapters are non-leveling. Use leveling on your dolly head.

Fit the webs on the bottom of Sachtler and Cartoni heads. These adapters are non-leveling - uses the leveling on the dolly head. Bottom fits standard Mitchell mount.

So named because it universally doesn't fit any one size perfectly but sort of fits 100 mm, 150 mm, and slot heads. Order the tiedown for your head separately.