The Draper 94255 Dual Reading Digital Dial Test Indicator features 3 function buttons The Draper 94255 is a Digital Dial Indicator, one of the most important measuring tools used in precision engine building. It is typically used to measure deck clearances, crankshaft thrust and straightness, indeed any measurement that involves the distance between two surfaces or small amounts of component travel. The digital readout includes both metric and imperial and features a lugged backplate for mounting on magnetic bases. Features: Rear mounting lug Powered by LR44 1.5V battery (supplied) Three function buttons - mm/inch, on/off and zero Specifications: Dial diameter: 55mm Range: 0.25mm / 0.1”