Ceramic Bearing Pulleys: The bike rear derailleur pulley wheels uses ceramic bearing, can reduce the resistance during cycling, which ensures fast and sensitive working. Improve riding efficiency 2023 New Upgrade Design: The design of positive and negative tooth shapes better fits the chain, reduces friction, and can effectively reduce chain dropout, resulting in smoother transmission Designed for 6-12 speed: This jockey wheel pulley is specially designed for 6-12 speed chains. It fits almost all mountain bikes and road bikes. In addition, it is also suitable for other bicycles with rear derailleur More Compatible: Made of aluminum alloy material, with upgraded CNC process. Fits SHIMANO SRAM Road Ultegra rear derailleurs How to Choose: Please choose the same size as your original pulley. If not totally the same, choose the smaller size, never choose the bigger than the original ones Bike Rear Derailleur Pulley Wheels