The Fowler 52-520-530 inch/metric dial indicator has a white American Gage Design (AGD) Group 2, 2-1/4" dial face with continuous and balanced dial readings, a 1"/25mm measuring range, 0.001"/0.01mm graduations, and a revolution counter, and is designed for taking measurements in machining, layout, and inspection work. The dial has black graduations for 0-100 continuous inch readings and red graduations for 0-100-0 balanced metric readings. A knurled bezel rotates 360 degrees to zero the reading at any location and has a screw clamp to lock the bezel in place. The lug back can be screw mounted.Dial readings with three digits, 0-10-0 for example, signify that the indicator has a balanced dial. Dial readings with two digits, 0-100 for example, indicate the dial has a continuous dial. Balanced dials are used for reading the difference from a specific surface reference point. Continuous dials are used for direct readings and usually have a larger measurement range than balanced dials. Specifications Dial type AGD Group 2, 2-1/4" diameter Dial reading 0-100 continuous and 0-100-0 balanced readings Range 1"/25mm Resolution 0.001"/0.01mm Bezel Knurled bezel with clamp rotates 360 degrees Mounting type Lug back Dial indicators are also called dial gauges, probe, and electronic indicators. These precision instruments measure small linear distances and object sizes. The dial magnifies the measurement so that it can be easily read by the human eye. Frequently used in manufacturing, laboratories, and other industrial or mechanical fields, dial indicators are used anywhere a small measurement must be found and recorded or transferred, such as checking the variation in tolerance of a workpiece. Standard dial indicators measure the displacement along the axis of the indicator. Dial test indicators are very similar to dial indicators, except that the axis of measurement is perpendicular to the axis of the indicator. Dial and dial test indicators can be analog, with a mechanical dial, or electronic, with a digital display. Some electronic models transfer the data electronically to a computer for recording and potential manipulation.The Fred V. Fowler Company manufactures inspection and measurement instruments such as electronic indicators, calipers, bore gages, and digital scales. The company, founded in 1946, is headquartered in Newton, MA.