Starrett Countersink Gauges are offered in three different angles so that the gauge sets on the angular side of the countersink, as opposed to a chamfer gauge which sets on the top edge of the chamfer. This gauge directly reads the large diameter of the countersink in 0.002" or 0.05 mm increments. A set master ring is furnished with each gauge for calibration and setting. Press the button on top of the indicator to firmly depress the gauge head into the countersink. When the gauge is removed, the indicator reading is held in place until the reset button is activated.