The crack measuring instrument is made of high-quality acrylic material, which is strong, smooth, wear-resistant, and not easily broken. Designed with highly transparent acrylic panels and easy-to-read measurement grids, the crack monitors are clear and precise. This tool is practical for monitoring the horizontal or vertical movement of cracks on flat surfaces. It supports 2D manual crack monitoring applications. Crack monitors are used to observe wall cracks and their development over time. The base plates are calibrated in millimeters and feature a transparent top plate marked with a cross-shaped thin line cursor for accurate readings. Material: Acrylic Color: Transparent Package Contents: 3 x Crack Measuring Instrument Note: Light reflection and different displays may cause slight variations in the color shown in the picture compared to the actual item. Measurement error allowance is +/- 1-3 cm.