GM 10-Bolt 8.5 8.6 Inch 3.42-4.88 Ratio Face Hobbed Ring Pinion Revolution Gear and AxleRevolution Gear and Axle ring and pinion manufactured to be compatible with GM 8. 5 Inch GM 8. 6 Inch differentials. GM 10 Bolt ring and pinions are manufactured with the same gear cutting processes as the OE brands, utilizing a Face Hobbed or 2 Cut gear cutting style followed by lapping. Face hobbed gears can be easily distinguished by the equal gear height from heel to toe. Face hobbed gears produce lower noise and increase load carrying capacity