The Shuriken oversized pulley system was engineered for maximum performance and designed to increase the efficiency of the drivetrain on any bike. The larger diameter of the pulley allows the oversized pulley system to rotate at lower RPM and reduces the articulation angle of the chain, lowering drivetrain friction. The TBT bearings inside the pulleys are filled with specially developed light grease to keep drag low to minimize drag. The carbon fiber cage and hardened steel / dura-aluminum hardware creates a light and strong foundation for the system. The pulleys are made of dura-aluminum and PVD (Physical Vapor Deposition) coated for long-lasting low friction and clean aesthetics. A purpose-specified tooth profile ensures crisp shifting and super smooth running. Upgrading to the Shuriken oversized pulley system allows you to add drivetrain capacity to a short cage derailleur, enabling you to run a larger cassette with an expanded range of gears. Thanks to its 12-19 tooth pulley size, a longer B screw is not needed. When properly installed and assembled, the Shuriken pulley system will improve the efficiency of any drivetin.