Micro drive cassette rear hub for Singlespeed and Dirt Jump Bushed driver for greater durability over cartridge bearings (bearings have to be smaller for micro drive, thus prone to higher loads) Forged 6061 aluminum shell, 2 main body sealed cartridge bearings No cog is included so user can choose the gearing that works best, 916t. Use HL-328* Tool HL3196 needed for cog removal International Standard 6bolt disc rotor mount CrMo M10 boltin fittings with 6mm anti-rotation hex fitting (helps when tightening wheel in frame) 14mm adapters included, 9/10/11/13/16t mini sprockets available separately