Fowler-Bowers XTD3 Digital Internal Micrometer These bore gages have been designed to further simplify the accurate measurement of bores. All XT instruments offer fixed anvils. Sizes above 1"/25mm offer extended travel. They are available as individual instruments or in complete sets. Includes Bluetooth Connectivity Package includes the following... Measuring Head Display Handle Setting Ring Features include... .250"-.312" (6-8mm) Measuring Range 0.00005" / 0.001mm Resolution 2.28" (58mm) Measuring Depth Large easy-to-read display.