Due to the limitation of mounting space, the structure of tension wheel and idler wheel bearings is normally very compact. When working in poor conditions, it is a severe test for normal work of tension wheel bearings by mud, water, sands and even corrosion at the range from -30℃ to 120℃. The tension wheel and its unit we provided have the characteristics of compact structure and stable performance, with the excellent sealing property in the use of more severe conditions. The product is coated with imported high performance grease that helps reduction of noise and improvement of service life.