Abstract: The internal geometry of tubes or pipes are tested by a measuring mandrel normally held in an adapter sleeve provided for end to end abutment with the tube or pipe to be tested; pressurized air is applied to the adapter sleeve to obtain the propelling of the measuring mandrel out of the adapter sleeve sleeve and into and through that tube or pipe; a tape, cable or rope is fastened to the mandrel and also wound on a drum to be unreeled therefrom as the mandrel is propelled through the tube or pipe to be tested; the drum is driven by a reversible drive operated for break operation tending to retard the mandrel and further provided for reversing permitting retraction of the mandrel back into the adapter sleeve after the pressure has been removed.