Features: Crack Gauges Monitors is crafted from acrylic material, so it is wear resistant, smooth, wear-resistant, and not easy to break. Crack Monitors is with a highly clear acrylic sheet and easy-to-read measurement grids, so it is clear and precise. It is very practical. You can use our Corner Crack Monitors to Monitors the horizontal or vertical movement of cracks on a plane. It is a precisions instrument. Because our Crack Monitoring Gauges can Monitors cracks in wall and how they evolve measured, it is very practical and convenient for you. The bottom plate of our Crack Measurement Tool is calibrated in millimeters. It also have a clear top plate, which is marking with a thin cursors in the shaped of a crossing. Specifications: Material:Acrylic Note: Please allow 1mm errors due to manual measurement. Due to the differences between different monitors, the picture may not reflect the actual color. Package includes: 1Set Crack Monitors