The driver features a Micro-Drive system that has 120 points of engagement which engage every 10 degrees.   The 4 included cog spacers allow you to position the cog where it provides the best chain alignment.  Hub set comes with a 16t Crupi Cog but is designed to work with any Shimano compatible cog and any Shimano type tool will remove the cog. 

• 24H hubset weighs 17.88oz (and is now discontinued)