Precision Steel Measuring Block Set Designed for accurate length calibration and inspection, for meters, calipers, and precision instruments. Standardized Length Measurement Tool Manufacture standards with tight tolerances, suitable for metrology labs and industrial toolrooms. Hardened Steel Construction Made from high-carbon chromium steel for excellent wear resistance and long-term dimensional stability. Mirror-Polished Surface Finish Each block is lapped to a mirror finish for superior wringing performance and minimal deviation. Secure Packaging for Safe Storage Comes in a protective case to keep blocks organized, clean, and ready for calibration tasks., Manufacturer: SOYWIM