Three self-centering anvils with precision contact points are used in the Mitutoyo Holtest mechanical three-point internal micrometre to measure the inside dimensions of bores accurately and efficiently. Three hardened-steel anvils uniformly placed at 120° on the Mitutoyo mechanical Holtest internal micrometre ensure precise alignment of the axis hole for accurate, repeatable measurements. Titanium Nitride (TiN)* is used to coat contact points for enhanced durability and precision. The ratchet stop mechanism of the holtest ensures a constant measuring force on the hardened-steel spindle, ensuring accurate and consistent measurements.