The Grade 5 ceramic Si3N4 balls will allow the bearing to be lighter and spin 50% faster than a traditional steel bearing. LD = Lube Dry Bearings have been clean and are free of all grease and Oils. Specifications: Bearing Material: Stainless Steel 440C, Ball Material: Ceramic SI3N4, ABEC#7/ISOP4 Enclosure: Two Seals, Enclosure Material: Rubber Seal Retainer Material: Stainless Steel, Radial Play: C0, Lubrication: LD Dry Lube (4) 3x6x2.5 Ceramic (1) 4x10x4 Ceramic (8) 5x8x2.5 Ceramic (1) 5x10x4 Ceramic (2) 5x11x4 Ceramic (2) 8x12x3.5 Ceramic (4) 10x15x4 Ceramic. NOTE: PHOTOS ARE FOR IDENTIFICATION ONLY Photos are for Seal / Shield / Bearing Style identification only and ARE NOT a photo of the exact bearing being ordered. Includes: 1 x SpeedTek RC Stainless Steel Hybrid Shielded CeramicBearing Kit for the MST RMX 2.0 KIT & RTR Versions.