This gear fits the Nikon 105mm f/2.5 AI 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.

This gear is very specific to this version of the lens. The Nikon Ai-S, AI, and pre AI lenses look very similar. You can double check which version of the lens you have by serial number here:

http://www.photosynthesis.co.nz/nikon/serialno.html

105