Those gauges are used with an outside micrometer for measuring inside diameter of bores and are extra long for gauging deep and shallow holes, slots and similar workpieces. The gauging surface of each piece is fully hardened to insure long life. Features -Color: Silver -Material: Carbon Steel -Size: About 9.20X1.00X0.50cm/3.62X0.39X0.20in - The non-slip handle, easy to measure, with a locking device at the tail, tighten them clockwise and loosen them counterclockwise. - Loosen the inner hole gauge, put them in the object to be measured, tighten them clockwise, and rotate turn to ensure it is tightened. - After the measurement is correct, tighten it clockwise and lock it. Use a caliper to measure the . (This product does not include calipers) - They are designed with compact size and light weight, easy to store. - They are simple in design, but very practical in use, which brings great convenience to you. Package list: 4 x Gauges