<p>This gear is purposed for Chinese M65x1 focusing helicoids with 17-31mm extension range.</p> <p>Please measure your helicoid outer diameter before purchase. Different versions of such helicoids available on market, and some of them may have different diameter.</p> <p>Installation is very simple - just slide the gear over the helicoid focus ring and tigth set screw gently. Set screw are installed, allen key is included into the delivery set.</p> <p>For sale is the gear only. The helicoid is pictured just to show how it looks with the gear installed.</p> <p> </p>