Features: Crack Gauge Monitor is constructed from premium-grade acrylic, providing excellent longevity, structural integrity, smoothness, and resistance to wear. Crack Monitor features a highly clear acrylic base paired with easy-to-follow measurement lines, making crack analysis accurate and effortless. You can use our Corner Crack Monitor to monitor the horizontal or vertical movement of cracks on a plane. It is a carefully designed instrument. Because our Crack Monitoring Gauge can monitor cracks in wall and how they evolve measured, it is very practical and convenient for you. Our Crack Measurement Tool features a millimeter-calibrated base and a clear top plate, incorporating a perpendicular reference line for precise alignment. Specifications: Component: Acrylic Package Includes: 2 Optional Package: Package 1 Include:2Pcs Crack Gauge Monitor Package 1 Include:4Pcs Crack Gauge Monitor note: Please allow 1mm errors due to manual measurement. Due to the differences between different monitors, the picture may not reflect the actual color of the item.