The Starrett PT22428 swivel post snug with dovetail clamp Is designed for use with Starrett 708, 709, and 811 series dovetail mount dial test indicators (not included). The snug fits 3/32 to 1/4″ diameter spindles and posts. The knurled thumb screw provides a secure grip when making adjustments. The snug is also compatible with Starrett 252 series height transfer gauge, 657 series magnetic base holders, and the 1/4″ rod of the PT22430 snug and rod unit (not included). Test indicator gauges, also called gages, are precision instruments that measure short linear distances. They are commonly used for detecting deviations from tolerance limits, such as small variations in flatness or height of an inspected workpiece, and permit measurement in narrow grooves or small bores. A test indicator gauge consists of a ball-tipped contact point on a levered arm, also called a measuring insert, which pivots from a hinge point. The reading indicates the degree of angular displacement of the arm. Test indicator gauges are commonly used in manufacturing, machining, and mechanical engineering. Standard test indicators measure the displacement of the arm perpendicular to the axis of the indicator. Dial and electronic indicators are very similar to test indicators, except that the axis of measurement is parallel to the axis of the indicator. 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 L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.