e*thirteen Helix Race Carbon e*spec Crankset - 155mm BOSCH CX Gen4/SX-Brose S Mag-TQ HPR50 26mm Offset Self Extractor BLKe*thirteen Helix Race Carbon e*spec Crankset 155mm BOSCH CX Gen4 SX Brose S Mag TQ HPR50 26mm Offset with Self Extractor Black. Helix Core cranks provide an e bike drivetrain upgrade with high end features and aesthetics at an exceptional value. Forged for e Enduro strength with alloy self extractor bolts pedal washers and molded impact boots. 24mm ISIS interface models are compatible with Bosch Gen 4 Brose S Mag TQ Fazua Yamaha Maxon and Specialized