Description: 4-step test calibration block for thickness gauges. Step values are more accurate and calibration is more reliable. Scope of application: for thickness gauges. High precision professional measurement. Specification: Material: iron Size: 80x19x20mm/3.14x0.74x0.78inch Package Includes: 1 Piece Thickness Test Block Note: The color may have different as the difference display, pls understand. Please allow 1-3mm error due to hand test.Thank you