The roller is a support wheel, but it is called differently. The roller is used to support the weight of the tractor and roll on the guide rail (rail chain link) or rail surface. It is also used to limit the track and prevent the track from sliding laterally. When the tractor turns, the roller forces the track to slide on the ground.

The drum is often in muddy water and dust and bears strong impact. Reliable sealing and wear-resistant rims are required.