TKI - TOM KOBZA INC Belt drive for the Ski-doo SUMMIT REV GEN4 2017-18 offers lighter weight , faster acceleration, and no broken chains and chaincases. Proven success and reliability on the Ski-doo XP, XS, XM chassis has rolled over into the new TKI GEN4 kit. This is a bolt-on turnkey, no modification upgrade every mountain rider should have. Most common ratios for the GEN4 Summit are 2.42 and 2.52. Specify gear ratio in the notes on ordering if there a different ratio you want that is not listed. Call if you need technical service for gear selection.