Fowler 52-224-103 inch digit micrometer set has a 0 to 3" measuring range and a flat anvil/spindle pair with a 0.256" diameter measuring face for general purpose measuring. The digit display has 0.001" graduation intervals and the secondary Vernier scale has 0.0001" graduation intervals and an overall accuracy of 0.00016" for precise readings. Microfine graduations on satin chrome finish provide clear reading, and the positive locking nut on the spindle locks measurements in place for accurate readings. A zero adjustment on the sleeve ensures accurate measurements. The anvil/spindle pair have hardened, precision-ground, and micro-lapped measuring faces with 0.00003" flatness and 0.00005" parallelism on 0 to 1" micrometers to provide accurate measurements. The spindle thread is hardened, ground, and lapped to provide smooth movement, accuracy, and long life. The ratchet-stop thimble provides an audible sound and stops turning when the spindle comes into contact with the workpiece, providing constant force for consistent measurements between operators. The grey baked-enamel frame provides durability and is heat-insulated to reduce temperature-related expansion or contraction providing for accurate measurements. The set includes 0 to 1", 1 to 2", and 2 to 3" micrometers, 1" and 2" standards, a wrench, and a fitted case. SpecificationsDisplay type Digit with Vernier scale Anvil/spindle style Flat Measuring range 0 to 3" Digit graduation interval 0.001" Vernier graduation interval 0.0001" Accuracy 0.00016" Thimble style Ratchet stop Anvil/spindle diameter 0.256" Flatness 0.00003" Parallelism 0.00005" on 0 to 1" micrometersMicrometers 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.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.What’s in the Box?Fowler 52-224-001 0 to 1" outside micrometer Fowler 52-224-002 1 to 2" outside micrometer and standardFowler 52-224-003 2 to 3" outside micrometer and standardWrench Fitted case