Seamless™ Follow Focus Gear for Sigma 18mm f3.2 XQ Multi-Coated LensThis gear fits the Sigma 18mm f 3. 2 XQ Multi Coated lens. It is designed specifically to fit this lens and is compatible with any standard 0. 8 Module follow focus. The gear sits 3 6mm high off the focus ring of your lens for a clean, low profile gear that slides smoothly onto your lens and into your current lens case. 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. 18