The Double Six single speed kit is our premium level kit featuring a 7mm wide spline base Shimano HG fit cog to ensure power transfer doesnt score or destroy alloy freehub bodies. Our tapered spacers are designed to offer increased lateral support for the cog under load.This kit is supplied with: 12t CNC Chromo 5/64 cog for micro drive set ups.2x CNC alloy spacers with laser etching.Lock ringShimano HG compatible only.13/14/15/16/17/18/19t cogs available separately.