Seamless™ Follow Focus Gear for Canon FD 35-105mm f3.5 LensThis gear fits the Canon FD 35 105mm f 3. 5 lens. Its 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.