Concentricity Gauge Arm Type Articulating Arm Base Height 9 21/25 in Base Length 3 5/64 in Base Size 3 5/64 in L x 3 5/64 in W x 9 27/32 in H Base Type Magnetic Base Width 3 5/64 in Compatible Indicator Mounts 3/8 in Dovetail Fine Adjustment Position Fine Adjust Top (FAT) Step Type None Working Length of Post/Lower Arm None Base Thread Size M8 x 1.25 Includes Dial Test Indicator Screw Type Knob Centering Arm Shank Size 3/8 in dia