The shaft is made of the cold drawn round steel, the bearing seat is made of the stamped steel plate of  high quality, the seal structure is PDC, with three sealing devices, and the performances in terms of dust prevention and water resistance are superior to those specified in national standard. After assembling, the rollers are characterized by the high strength, small radical play eccentricity, small resistance to rotation, light weight, low energy consumption, long service life of more than 30000 hours.