Fowler 52-275-002-1 Inside Micrometer, 1-2" Measuring Range, 0.001" Graduation, +/- 0.0002" Accuracy. Microfine graduations (.001" or .01mm) on a satin chrome finish permit easy reading. With Fowler Inside Micrometer, you are assured of smooth operation and stabilized uniform accuracy. The frame is specially designed to enable the micrometer to provide extremely accurate small internal measurements. Measuring faces are fully hardened, precision ground and microlap finished to assure exceptionally accurate measuring. Ratchet stop thimble assures exact and repetitive readings. Easy zero adjustment on the sleeve. Meets or exceeds Federal accuracy specs. Fowler 52-275-002-1 1-2" inside micrometer comes with a setting ring, a spanner wrench and a case. Fowler 522750021inside micrometer comes with setting ring, a spanner wrench and a case. Micrometers are precision measuring instruments that use a calibrated screw to measure 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.