e*thirteen Helix Race Cassette - 12-Speed 13-52t Graye*thirteen Helix Race Cassette 12 Speed 13 52t Gray. The e*thirteen Helix Race 12 speed 13 52t cassette features close ratio gearing specifically engineered for steep terrain where climbing time and shift frequency is high and descents are gravity driven. By placing more gears where riders spend the majority of the time they can optimize cadence and torque for improved climbing efficiency with smoother shifts under load for both analog and eBikes.