Ready to experience total drivetrain optimization? Introducing Kogel Kolossos bringing low friction and precise shifting to GRX 12-speed gravel bikes with this oversized derailleur cage. This upgraded cage fits mechanical12-speed RX820 series drivetrains for Shimano GRX 1X rear derailleurs featuring large pulleys 18-tooth narrow-wide bottom and 14-tooth top and constructed with their strongest cage design yet.