SRAM Rival eTap AXS Rear Derailleur - 12-Speed Medium Cage Battery Sold Separately BLK D1SRAM Rival eTap AXS Rear Derailleur 12 Speed Medium Cage Black D1. On any surface you can imagine in any drivetrain configuration the SRAM Rival eTap AXS Rear Derailleur can handle it. Secure chain management and fast precise shifting make for a smooth and quiet ride every time. Wireless electronic eTap shift logic for intuitive shifting easy setup and reliability Compatible with both 1x and 2x drivetrains 36t cog max derailleur works with 10 28 10 30