JINHU Group offers haul-off unit with 2-Caterpillars as well as with Multi-Caterpillars. Haul-off unit / tractor is used to provide necessary force to pull the pipe through the entire cooling operation without affecting the dimension of the pipe. Haul-off unit also provide a constant pulling rate to maintain the proper wall thickness of finished product. Wall thickness of the finished plastic pipe is determined by the combination of puller speed and extruder screw speed. At a constant screw speed, increasing the puller speed cause reducing the wall thickness while decreasing puller speed will increase the wall thickness of plastic pipe.