Seamless™ Follow Focus Gear for Zeiss 21mm f2.8 ZF LensThis gear fits the Zeiss 21mm f 2. 8 ZF lens. It is designed specifically to fit this lens and is compatible with any standard 0. 8 Module follow focus. This gear uses a specialized design so it will slide past the aperture ring and onto your focus ring without removal of any parts of the lens. 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. 21