Bearings are provided with ample lubrication for extended periods from oil seeping with a polyolefin resin for excellent performance in water and dust contaminated environments.These rolling bearings are provided with self-lubricating molded oil, which provides ample lubrication from oil seeping from a polyolefin resin These bearings provide excellent performance in dust-contaminated environments. A stainless steel series of this bearing is also available for environments where there is heavy exposure to water contamination.