Precision Gauge Block Set Designed for accurate calibration of calipers, micrometers, and other precision measuring tools. High-Grade Hardened Steel Construction Made from wear-resistant alloy steel for long-term dimensional stability and durability. Mirror-Lapped Surfaces for Reliable Wringing Blocks are ground flat and parallel with smooth surfaces for consistent stacking and minimal deviation. Conforms to Standards Manufactured to Grade 1 accuracy for professional use in labs, workshops, and inspection . Protective Storage Case Included Comes in a foam-lined case for organized storage, safe transport, and quick access during calibration tasks., Manufacturer: ZKLGS