opposing rotor sidewalls of a disc brake rotor which when properly extended point upward away from the user 39 s feet or chest when the device 10 is in the hands of the user in the as used position taking a rotor thickness measurement brake drum interior measuring jaws 14 which are employed for measuring a brake drum diameter between opposing walls as depicted in fig2 will point the opposite direction of the exterior measurement jaws 12 when the device 10 is in the as used position with the user taking a measurement of the interior diameter of a brake drum 13 the digital display 16 is visible directly to the eyes of the user in the as used position whether the rotor not shown is perpendicular to a surface upon which it rests or is in the jaws of a vice the digital display 16 is also visible directly to the user during a measurement of a drum 13 the digital display 16 provides a calibrated means for axially adjusting either the distance of the exterior measurement jaws 12 or interior measurement jaws 14 from each other and indicating the extent of movement or distance thereof or therebetween from a normal u201c zero u201d position which can be set by pressing the zeroing button 23 indica on the digital display 16 is always right side up to the user during all measurements taken in the as used position one unique construction aspect of the device 10 allows the drum 13 to be supported on a surface such as a table or floor during this procedure with the opposing sidewall edges 15 of the drum 13 extending away from the support surface both the.