Ceramic-hybrid bearing features deep-groove design 52100 High-Carbon Chromium alloy races, with grade 5 Silicon-Nitride Ceramic balls, ultra-low drag VV dual-lip seals to withstand the outside elements, and to contain the 90% fill Kluber NBU52 ultra-smooth and sticky, water-proof grease. Ceramic balls reduce bearing wear and increase bearing life by eliminating steel on steel contact within the bearing. VV seals are our lightest contact design, allowing for the fastest spinning bearing we make, though not as protective against the elements as our LLB or LLU type seals.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.Bearing Code: MR 15307Dimensions: 15mm x 30mm x 7mmABEC: 5Grade: 5Seals: LLU/LLBGrease: Kyodo Yushi PS-2Application: Hubs, Bottom Brackets