e*thirteen Helix Race Alloy e*spec Crank Arm Set - DUB 12mm Offset 160mm with Self Extractor Black. 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.