Developed and designed entirely by CeramicSpeed, the Oversized Pulley Wheel System for Shimano is advanced for the optimization of bike performance. Everything from bearings to the cage is made from the highest quality materials. The oversized aluminium pulley wheels are fitted with standard or coated CeramicSpeed Bearings, which reduce friction to the minimum. The overall power savings of the OSPW System for Shimano reach 30%-60% or more in some cases. The OSPW System has a lifetime that lasts 3-5 times longer than the commonly used standard pulleys on the market. The OSPW System for Shimano comes as two different systems, one compatible with Ultegra (6700/6770/6800/6870) and Dura Ace (7900/7970/9000/9070), 10s and 11s, electric and mechanical groupsets, and another compatible with the Shimano 9100/9150 and 8000 series - EXCEPT the R8000 GS. While the first option features a set of two 17-tooth pulleys, the OSPW System for Shimano 9100/9150 and 8000 features an optimal 13/19-tooth combination specially developed to fit the design of the derailleur. 

Find a list of compatability for OSPW for Shimano 9100/91500 and 8000 series here 

IMPORTANT: When travelling, please remember to dismount your entire rear derailleur with an Allen key, as the OSPW System will not fit in most bike travel bags and could be damged if left on.