Mitutoyo Holtest Type II Internal Micrometer The Mitutoyo Holtest is a versatile, self-centering three-point internal micrometer for the accurate and efficient direct-measurement of internal diameters. Three anvils, evenly spaced at 120° apart, contact the internal wall surfaces and find true alignment with the axis of the bore for accurate ID measurement. Specifications Include... 3.00" - 3.50" Measuring Range 0.0002" Graduations +0.00015" Accuracy Features Include... Hardened Steel Measuring Contact Points provide excellent durability allow the instrument to measure close to the bottom of a blind hole. Measurement can be taken closer to the bottom of the blind bore. Can measure deep holes using an Extension rod (optional). With Ratchet Stop for constant force. Setting Rings for zero point adjustment are optional. Supplied in fitted plastic case.