With these BBB Cycling BDP-07 RollerBoys 12-Speed derailleur wheels you can make your SRAM drivetrain run like clockwork again. These 12-tooth derailleur wheels are specially designed for SRAM 12-speed MTB groupsets. The Rollerboys have a narrow-wide grind, which keeps the chain well in place while shifting. The wheels themselves are made of a composite mixture to which 40% glass fibre has been added for even better durability. In addition, the Rollerboys bearings are sealed, so moisture and dirt are not an issue for these derailleur wheels. Durable and strong composite material BBB Rollerboys derailleur wheels are made of a composite material, which contains 40% fibreglass. The fibreglass provides a very stiff and durable material, which is less prone to wear and tear. This is why these derailleur wheels keep their optimum grip on the chain for a long time! Sealed bearings When cycling in mud and rain, it is very important that your bearings keep running smoothly. To prevent premature wear from dirt or water, BBB has put well-sealed bearings in these Rollerboys. Because of this you can expect many miles of smooth-running wheels, also in bad weather conditions!