Abstract: Rolling bearings are proposed in which acoustic deterioration is suppressed which maintaining low dust, low torque and long life. Also, a grease for rolling bearings is proposed which is less likely to scatter under centrifugal force at high speed rotation, whereby preventing malfunction and noise of electronic information devices. A lubricating oil film of an ester-series oil having a dynamic viscosity at 40° C. of 35 mm2/s or over is formed on the friction surface of a rolling bearing. There is also provided a high-speed rolling bearing in which a lubricating grease having its worked penetration (JIS K2220) adjusted to 175-250 is retained therein. The grease is preferably prepared by adding a thickening agent containing 50 wt % or more of an aliphatic lithium salt 12-24 in carbon number to a base oil comprising 30 wt % or more of an ester oil having a dynamic viscosity at 40° C. of 10 mm2/s or over, and having its worked penetration (JIS K2220) adjusted to 175-250.

Abstract: A rolling contact bearing includes an inner race (1), an outer race (2) accommodating therein the inner race (1), and a plurality of rolling elements (4) interposed between the inner and outer races (1, 2). An insulating covering (8) made of an elastic material having an electric insulating property is mounted around the outer race (2). This insulating covering (8) includes a cylindrical body (8a) and collars (8b) extending radially inwardly from opposite ends of the cylindrical body (8a). This cylindrical body (8a) in a natural condition has an inner diameter smaller than an outer diameter of the outer race (2), but in an assembled condition with the insulating covering (8) placed around the outer race (2) against its own elasticity, the cylindrical body (8a) is held in tight contact with an outer peripheral surface (2a) of the outer race (2) and the collars (8b) are held in tight contact with respective opposite end faces (2b) of the outer race (2).