An inside micrometer is a type of precision measuring tool used to measure the internal dimensions of cylindrical or round objects. It consists of a long, slender shaft with a spindle at one end that is inserted into the object being measured and a measuring mechanism at the other end. The spindle is rotated to apply pressure to the inside of the object, and the measurement is read from the scale on the outside of the tool.

Inside micrometers are commonly used in manufacturing and engineering applications to measure the internal diameter of holes, tubes, and other cylindrical objects with high accuracy. They are available in different ranges and resolutions to suit different measuring needs, and can be used to measure objects with diameters ranging from a few millimeters to several centimeters.

Inside micrometers typically provide highly accurate and repeatable measurements, and are made of durable materials such as steel or carbide to withstand repeated use in a workshop or industrial setting.