The Jockey Wheels XD15 Ceramic - Shimano GRX 11sp by Enduro Bearings is the ultimate upgrade for your bike. These machined Delrin Derailleur Pulleys feature XD-15 Ceramic-Hybrid, radial bearings for enhanced shifting performance and longevity. Designed and manufactured for performance, these pulleys have CN bearings in the upper pulley for maximum shifting accuracy and C4 bearings in the lower pulley for chain-line movement.These pulleys are made from 500 AF Delrin material, which is highly durable, rigid, and smooth. Compared to pulleys made from aluminium or titanium, the Delrin material provides significantly less drag, resulting in improved performance on the bike.An exclusive feature of Enduro Bearings, the XD-15 Ceramic-Hybrid bearings are corrosion-proof and have cryogenically treated nitrogen steel races with Grade 3 ceramic balls. The deep-groove design raceways allow for maximum-sized ceramic balls, improving performance and longevity. The Kluber NBU52 grease used in these bearings is highly resistant to being washed out and ensures the pulleys run smoothly.These jockey wheels are designed as an upgrade for most 11 speed Campagnolo derailleurs. Enduro Derailleur Pulleys are available in different configurations, with the XD-15 Ceramic-Hybrid being the top of the line. All Enduro pulleys are proudly precision manufactured in the USA.Compatible with Shimano GRX 11sp. Bearing Grade: XD15 Ceramic. Enduro Part Number: BKCJ-0351.