This gear fits the Zeiss 135mm f/2.0 APO Sonnar lens. This will ONLY fit the APO version of this lens. Please double check (there's an older non - APO version too). The gear is sufficiently wide to cover the full range of travel of the focus ring. 

It’s specially designed to fit this lens and is compatible with any standard 0.8 Module follow focus unit. Focus gears are generally slim for a clean, low profile gear that slides smoothly onto your lens and into your current lens case. Custom spec gears can be made on request. The gears do not have to be removed after each use although you can if you like. Each gear comes with a lifetime of support.

135