The material is 20CR or 40Cr. As for the 20CR, it adopt carburization and quenchhardening. The carburized depth is 0.8 1.2mm, the surface hardening is HRC53-58, 40Cr adopt whole quenchhardening, after tempering, the hardening is HRC45-48, the surface is treated with phosphating,BUSHING specification can be customized.