Increases RPM up to 216 RPM in 6th gear @ 70 mph, more in lower gears, for more grunt and a stronger pull. Includes required custom length 88t primary chain. The primary chain sprockets on the OEM clutch basket are 46 tooth in stock applications. Good for cruising but some find them over-geared. Evolution Industries has this 49 tooth primary chain sprocket, which must be installed on the clutch basket, and includes the required custom length primary chain. It will increase RPM in each gear and give more torque and horsepower, for better engine reaction and two-up, head wind or up-hill performance. Note: See 552032 Counter bore tool. Used to counterbore OEM clutch baskets to install the 46/49 tooth Evolution Industries basket sprocket & ring kits