CeramicSpeed Shimano OSPW System. Features: Proven to be the fastest pulley system, chosen by many of the world's leading cycling teams and professional triathlete Optimized tooth designs offer 3-5 times longer life than standard OE pulleys Coated: metallic layer that covers bearing races making them 75% harder than steel. Even lower friction and highly resistant to corrosion Standard: low drag with hardened steel races and ceramic ball bearings 9100/9150/8000 SS/8050SS is not compatible with 8000-GS or 8050-GS, use Shimano 11sp system 9100/9150/8000 SS/8050SS is not compatible with RX800/805, use Shimano RS80/805 system In the box: complete upper and lower OSPW system, 15ml CeramicSpeed Bearing Oil dropper bottle Specs: Model:standard Fitment:12sp XTR/XT Upper Lower:14/18 tooth Color:black