This large diameter RD CAGE is compatible with MTB and gravel (SHIMANO GRX) using the upper 12T (E28) and lower 18T for gravel/MTB. The cage plate design has been updated compared to the previous MTB cage "C48". It has been reborn into a fearless image while providing increased rigidity and reduced weight. The upper pulley is compact to optimize transmission performance while reducing load on the rotational axis for better power efficiency. The carbon pulley not only reduces chain noise, but also features a unique narrow wide design X-ODON technology on the teeth for smooth transmission and wattage savings. Features: Large diameter pulley reduces load and provides greater power efficiency. The end of the pulley uses a unique narrow wide design "X-ODON" technology for smooth transmission and reduced wattage. Compact upper pulley optimizes transmission performance. Carbon pulley reduces chain noise pulley number of teeth / Material: 12 x 18T / Carbon Cage: Normal Cage Material: Carbon Composite Bearing: Ceramic RD Type: MD1R. D Compatible Models List The situation may vary in different environments such as the size of the XTR M90xx, XT M80xx, SLX M7000, GRX RD-RX812/817 pulley and the number of sprocket teeth, as well as the design of the frame and chain length. We cannot be able to answer any questions, such as whether or not it can be used or compatible. Installation and maintenance required by a professional shop with knowledge. Please consult a specialist with knowledge for fitment and installation. The full ceramic type uses both the ball/lace and has a seal-less construction. Regular cleaning of bearings is required to maintain performance. Please be careful.