Helix Race 12-speed, 556% Range, 384g More Range, Less WeightThe HELIX Race Cassette is an upgrade to any SRAM™ Eagle™ or Shimano™ drivetrain*, with more range than any other cassette on the market. 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. PRODUCT FEATURES Compatible with SRAM™ and Shimano™ 12 speed drivetrains 2-piece design allows for replaceable aluminum cogs E*spec uprated for E-bike use RIDER BENEFITS Reduces un-sprung rear wheel weight for improved suspension function and handling Excellent shifting with Shimano™ and SRAM™ systems without compromise e*thirteen’s wider range and 9 tooth cog allows riders to run a 2 tooth smaller chainring for more clearance and reduced weights *XD™ driver required.   Hope XD drivers are undersized at the clamp location and require a Cassette Shim Kit that is included with the 9-50T cassette in the box.