These hole gages will check hole diameters to . 001" and 0. 02mm. They are fast, accurate, easy to read and have a balanced design for easy one- hand operation. The gage can be pressed down on a flat surface and checked so the size should read the same as the set number stamped on the back of the indicator. It can also be checked and set with an optional "setting master". All ground surfaces are of hardened tool steel. Indicators are AGD design. Holes that need to be accurately checked must have no chamfers or countersinks.