The e*thriteen Helix Race 12-speed 9-52t cassette is engineered to deliver precision shifting performance with an industry leading 578% gear range. The proprietary 9 tooth smallest cog combined with the 52t largest cog enables the use of a smaller chainring for improved clearance, lighter system weight and a lower bail out gear ratio without high gear compromise. - Seamless cross-compatibility with Shimano, SRAM, and TRP 12-speed drivetrains - Patented 2-Part design provides strength, stiffness, light weight, and ease of service - Aluminum and steel clusters can be replaced separately to reduce service cost - 9 tooth high gear allows use of smaller chainrings for clearance and weight savings - Fits XD(TM) and XDR(TM) Drivers Only (Hope XD drivers are undersized at the clamp location and require a Cassette Shim Kit -Sold Separately) - Tested extensively for analog and e-bike use