At e*thirteen, we're always striving to bring something new to the table. That's why we created the Helix cassette line - to offer unparalleled cross-compatibility without sacrificing performance.As e-bikes have become more popular, we set out to engineer a close-ratio cassette specifically for them. Enter the Helix R - a new 12-speed close-ratio cassette, specifically engineered for steep terrain where climbing speeds are high, and descents are gravity-powered.Key Features:Close ratio gearing cassette for better cadence and improved shifts under loadLower fatigue and extended range (Bio or Battery) with sweet spot cadence for max efficiencyHelix R 13-15-17-19-22-25-28-32-36-40-45-52 vs Eagle10-12-14-16-18-21-24-28-32-38-44-52Cross-compatibility with Shimano, SRAM, and TRP drivetrains and chainsAluminum and Steel clusters can be replaced separately to reduce service costPatented two-piece aluminum/steel construction for strength, stiffness, light weight, and durabilityReinforced for