Features1Lightweight and Sturdy: Tailored for mountain and road Bikes, the ceramic rear derailleur pulley wheel features an aluminum alloy construction with a hollow design, ensuring a smooth and efficient riding experience. 2Strong Compatibility: The new card spring structure prevents chain jamming, suitable for 8, 9, 10, 11 speed rear derailleurs, with an outer diameter compatible with 4, 5, 6mm, offering flexible rotation and noiseless operating. 3Dual Function Design: Compatible with both pulleys and tension wheels, this derailleur pulley wheel utilizes a card spring fixing structure, ensuring smooth operating whether used for pulleys or tension wheels. 4Slick Rotation: Equipped with zirconia ceramic balls for self lubrication and no maintenance performance, the rear derailleur pulley wheel rotates seamlessly, providing an exceptionally smooth riding experience. 5Enhanced Transfer Efficiency: Effortlessly pedal with the latest card spring fixing structure, eliminating chain jamming issues, ensuring slick gear changes for a stable and efficient ride.SpecificationItem Type: Ceramic bearing guide wheelMaterial: Aluminium Alloy, CeramicPackage List1 x DerailleurPulleyWheel2 x Reduction Sleeve