1) Sliding contact surfaces: Steel vs. Steel. 2) Materials: Both outer race and inner race are made of high chrome bearing steel. 3) Heat treatment: Both outer race and inner race are quenched (hardened), surface phosphorized. 4) Features of structure: With oil groove and oil holes, with an axial split in outer race. With dual seals. 5) Lubricant: molybdenum disulfide. 6) Properties: Good wearability, corrosion resistance, self-alignment, dust proof.