Intermediate Ring: A separable ring in a roller bearing with two or more rows of rollers that isolates and guides the two rows of rollers. Powder metallurgy middle retaining ring: the series middle retaining ring produced by powder metallurgy process has replaced the steel middle retaining ring. Its material organization is: pearlite + graphite + cementite + pores. The high-hard particles of the middle retaining ring are distributed on the softer matrix, and together with the solid lubricant in the matrix and the lubricating oil in the pores, form a special anti-friction-wear-resistant material, and its wear-resistant life is increased by more than 9 times. Generally, the outer diameter is less than 200mm and the wall thickness is more than 2mm.