- These chainrings from KMC are suitable for Bosch 4th generation motors. Guaranteed to last a minimum of 3500km, combining these with KMC's E chains to extend the life of your chain and chainring even further. Longer lasting, quality material and unparalleled gear changes. **Features** * Perfectly tailored to narrow KMC chains * Hardened CrNo steel * High efficiency, saves battery * Extreme durability, highest precision * Simple conversion * Perfectly matched with KMC Chains **Tech Specs** * Size: 1/2" X 11/128" * Colour: Black * Treatment: Hardened Chromoly steel * For Bosch 4 systems * Direct mount: 9mm offset * E1, E12, E11, E10, E9 & E8 chains