Mechanical tubular-rod inside micrometers and sets are used to measure the inside dimension of holes, tubes, pipes, and other parts. These micrometers are used with interchangeable tubular rods that are connected to the micrometer and inserted into bore holes or openings. The ratchet thimble on the body of the micrometer is adjusted until the rod makes contact with the surfaces being measured. When the micrometer is locked and extracted from the hole, the user reads the vernier scale and adds the length of the rod or rods being used to determine the overall inside diameter. The tubular rods are hollow and lightweight and are commonly used by mechanics and machinists for large-diameter applications where a lighter weight tool is an advantage.