The Mitutoyo 139 series tubular vernier inside micrometer includes a set of extension pipes with anvils for a diversified range of measurement measuring inside dimensions (ID) of cylinders, rings, and parallel surfaces. It has a vernier scale in inch units for taking precise ID measurements to 0.001”, and a satin chrome rust- and glare-resistant finish. The micrometer head has a travel of 1” per revolution that helps provide quick positioning. The hollow, tubular extension pipes help provide light weight with rigidity. A locking clamp helps hold measurements in place. The micrometer and accessories come with a fitted case for storage.Micrometers are precision measuring instruments that use a calibrated screw to measure small distances. These measurements are translated into large rotations of the screw that are then able to be read from a scale or a dial. Micrometers are typically used in manufacturing, machining, and mechanical engineering. There are three types of micrometer: outside, inside, and depth. Outside micrometers may also be called micrometer calipers, and are used to measure the length, width, or outside diameter of an object. Inside micrometers are typically used to measure interior diameter, as in a hole. Depth micrometers measure the height, or depth, of any shape that has a step, groove, or slot.Mitutoyo manufactures precision measuring tools, metrology equipment, and systems. The company was founded in Tokyo in 1934 and formed Mitutoyo America Corporation in 1963, which is headquartered in Aurora, IL.