The operation of the gauge is based on the principle of laser scanning of the inner surface of the pipe by a rotating laser head. To achieve the required accuracy, the range of controlled diameters is divided into two sub-ranges controlled by independent laser triangulation sensors installed in a rotating head. The gauge also contains removable supports (two sets) designed to install the gauge on the end of pipes of different diameters. The rotation of the laser head is carried out by a built-in motor. The gauge is equipped with a display to show the results.