1-2-3 MicroGage Ultra precision 1-2-3 Block is hardened steel, ground to +/- 0.0002 inches. Dial Indicator has 1.0 inch travel, with 0.001" accuracy. Comes with round tip. Includes a 3/8" flat Dial Indicator tip, for measuring shafts and/or jointer knives 2 Rare Earth magnets holds the Dial Indicator Carriage to the 1-2-3 Block Lock Screw secures the Dial Indicator at any desired position