6pce Telescoping gauge set with knurled handles and locking nuts, automatically self centring plungers with constant spring tension, providing uniform contact pressure. Use for quick inside measurement of cylinders. Indirect measurement by outside micrometer. Size contents: 8 - 12.7, 12.7 - 19, 19 - 32, 32 - 54, 54 - 90, and 90 - 150mm