Doosan Excavator Dh80 Track Roller For Dx140lc 2270-P1061, Dh55 Excavator Bottom Roller The supporting roller is often in the lower part of the track, and the track is supported upward, so that the track ensures a certain tension and prevents deviation and deviance.It is widely applied in bulldozers and excavators Caterpillar, Komatsu, Hitachi, Kobelco, Kubota, Yanmar and Hyundai etc. Our products are according to the standard of OEM to manufacture.