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 device is practical for monitoring the horizontal or vertical movement of cracks on flat surfaces. It supports 2D manual crack monitoring tasks. 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 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 the color of the item in the picture to appear slightly different from the actual product. Measurement error allowance is +/- 1-3 cm.