When making an installation, the easiest way is to use a mole with a diameter that corresponds to the diameter of the installation being made. With a larger mole we make larger diameters, with a smaller one we make the smaller ones. However, in a situation where we have occasionally to make installations with diameters larger than the diameter of the mole we have, expanders/calibrators can help us. They have a larger diameter than the piercing machine they are designed for. By putting them on the mole, we can make installations with diameters larger than our mole. However, we must remember that widening the hole with an expander must be preceded by making a so-called "pilot" borehole, using the mole itself.
In order to expand boreholes with simultaneous installation of pipes, the following are necessary: a towing tip, a towing tool, an extending rope for towing tool.
You can find more information on how to do the work with different accessories here.