SPI Dial Test Indicator and Magnetic Base Stand Dial Test Indicator Features... Range: 0 - 0.030" Reading: 0-15-0 Contact Point: 0.080" dia. X 1/2" long Graduation: 0.0005" 2 dovetails: 3Æ’??8" and 1Æ’??4" dia. Certificate of Calibration . Magnetic Base On / Off Switch Clamp Assembly Includes two holding rods and 2 clamps that accept 3Æ’??16" and 1Æ’??4" diameter rods