A dial bore gauge is a precision measuring tool used to assess the internal diameter of cylindrical objects, such as engine cylinders or pipes. It features a dial indicator that displays measurements as the gauge is inserted into the bore, allowing for accurate readings of size and roundness. These gauges typically consist of a long, slender body with a measuring head that expands to contact the inner surface of the bore. They are essential in machining and quality control processes, ensuring that parts meet specified tolerances and maintaining the performance of mechanical systems.