Measure the focus ring of your lens, type its diameter or one full tape circumference, pick a width and download a slip-on follow focus gear. Opening, outside diameter and width are engraved inside every ring.
What you set
Lens diameter from 40 to 110 mm, or the circumference measured with tape
Ring width from 10 to 40 mm
Automatic wall, a wall thickness from 2 mm, or one outside diameter for all your lenses
What you get
One STL with standard module 0.8 teeth for follow focus units and focus motors
Opening, outside diameter and width engraved inside