More informationRollerBoys Ceramic 12T srRollerBoys, the 12x12T ceramic derailleur hubs. Made of high-performance composite material by EMS Swiss, they are composed of 40% fiberglass. This makes our RollerBoys durable and efficient. Equipped with sealed bearings, lubricated with ceramic oil for reduced resistance, and protected by an aluminum cover, these pulleys guarantee optimum long-term performance. RollerBoys integrate perfectly with SRAM 12-speed road groupsets, guaranteeing a smooth, precise cycling experience.12x12T ceramic derailleur pulleys.High-performance composite material from EMS Swiss with 40% fiberglass.Sealed bearings with aluminum cover for maximum durability.Specially lubricated with ceramic oil for lower resistance.Compatible with SRAM 12-speed road groupsets.