Bearing NO.: SMR74C-2OSRings Material: 440C Stainless SteelBalls Material: Si3N4 CeramicInner Diameter: 4mmOuter Diameter: 7mmWidth: 2.5mmPrecision: ABEC-7(P4)Seal Type: Orange Rubber SealsLubrication: Self-Lubrication(No grease or oil)Feature: High speed, Corrosion resistant, Rust prevention, Dry lubrication, insulation.Application: Fishing Reel, RC Car, Mini Tools, Small Motors, Home Appliances, ... etc. SMR74 2RS 4x7x2.5 Hybrid Ceramic Bearing MR74 SMR74C 2OS CB 4*7*2.5 mm Stainless Steel Ceramic Ball Bearing