E*thirteen Helix Race 12sp Cassette 9-50t - Nickel Graye*thirteen Helix Race Cassette 12 Speed 9 50t Nickel Gray. The e*thirteen Helix Race 12 speed 9 50t cassette is an upgrade to any SRAM Eagle or Shimano drivetrain and offers a 556% range. The 9 tooth cog lets you step down one chainring size while keeping the same top end gearing and provides not only better ground clearance but an overall lighter drivetrain. Works flawlessly with Shimano and SRAM drivetrains including electronic shift systems CNC