The Starrett 124MA solid-rod inside micrometer set offers a range from 50 mm to 200 mm and is graduated at 0.01 mm intervals. The hardened, radius-ground anvils on rods are accurate. Solid-rod inside micrometers are often used for measuring the inside diameter of a cylinder or ring and when measuring parallel surfaces. The micrometer head, rods, and spacing collars are assembled to the desired range and then adjusted to obtain the measurement. 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. The L. S. Starrett Company was founded in 1880, originally manufacturing bench vises, squares, and other tools. They acquired other companies throughout the years, expanding their services into making precision measurement instruments and tools, such as calipers, micrometers, saw blades, and gauges. Starrett is headquartered in Athol, Massachusetts and has manufacturing facilities in Brazil, the United Kingdom, China, and other locations.