Magnetic base with on/off lever powerful magnet rated at 176 lbs holding for flat or round surfaces. Flexible adjustable shaft arm with lever lock and a length of 12 inches. Can install a round shaft on the end of flex arm up to 1/2″ diameter. Easy to read 2-1/4″ white face with black markings reads in .001″ increments 1 inch travel AGD indicator. Great for measuring runout on brake rotors, crankshafts, camshaft end play, degree camshaft and more. Comes with hard plastic storage case. Please e-mail with questions.