E*Thirteen Helix Race Alloy E*Spec Bosch Gen4 Brose S Cranks An E-Bike Drivetrain Upgrade The Helix Race Alloy Cranks are a high-performance, weight-optimized alternative to carbon fiber for riders who prefer alloy cranks. These 24mm ISIS interface cranks are engineered for compatibility with Bosch Gen 4, Brose S Mag, TQ HPR 50, Fazua, Yamaha, Maxon, and Specialized Brose motor systems. They come in short lengths starting at 155mm for improved pedal clearance and are tested to E-Enduro standards. Features Material: forged, CNC-machined AL-6066-T6 arms Compatible with 24mm ISIS spindles Available in short lengths from 155mm for improved pedal clearance SPECIFICATIONSSpeeds11/12-Speed BB Compatibility24mm ISISChain Ring Sold Separately Crank Arm Length155, 160mm BB Spindle Interface24mm ISISChainring Material N/ABolt Center Diameter (BCD)-Crank Arm Material Forged, CNC Machined AL-6066-T6Chainline26. 5mm Offset Bottom Bracket Included No Intended Usee-MTBWeight- | E. thirteen | Helix Race Alloy E*spec Bosch Gen4 Brose S Cranks 155Mm Offset Blk 26. 5Mm Offset | Aluminum