An Enduro Bearings exclusive, our XD-15 Ceramic-Hybrid bearings combine corrosion-proof, cryogenically treated nitrogen steel races with Silicon Nitride Grade 3 ceramic balls in a proprietary process that results in the ultimate high performance bearing setup. The deep-groove design raceways allow for maximum sized Grade 3 Silicon Nitride ceramic balls for for increased contact area and improved performance and longevity. Dual-lip labyrinth (LLB) seals protect from the elements, and contain the 90% fill Kluber NBU52 grease that runs smoother with time and is highly resistant to being washed out.The most impressive feature of XD-15 ceramic-hybrid bearings is, unlike other bearings, they only get better with time and use. As the bearings wear-in, the super-hard ceramic balls actually make the XD-15 races even smoother. So, when compared to other ceramic-hybrid bearings on the market that claim speed and power advantages on day one, Enduro XD-15 bearings not only provide the same initial advantages on day one, but will become faster and smoother with time and use, while the other ceramic-hybrid options will only get slower. We are so confident in the performance of XD-15 Ceramic-Hybrid bearings.This size bearing is used primarily in hubs.The Enduro line of bearings are available in High-Carbon Chromium Steel, 440C Stainless Steel, Ceramic-Hybrid and XD-15 with Ceramic or Stainless Balls. Our bearings are always engineered with deep groove races to accommodate the largest balls possible. All of our standard bearings feature dual-lip seals that ride in a micro groove creating a full labyrinth to provide ultimate protection against the elements.Specifications:- Outside Diameter: 18mm- Inside Diameter: 30mm- Width: 7mm- Material: XD-15 Stainless Ceramic