The crack measuring instrument is made of high-quality acrylic material, which is durable, strong, smooth, wear-resistant and not easy to break. Designed with highly transparent acrylic panels and easy-to-read measurement grids, our crack monitors are clear and precise. This is very practical for you. You can use our corner crack monitor to monitor the horizontal or vertical movement of cracks on a flat surface. It is a precision instrument. Tell the story of 2D manual crack monitoring work. Crack monitors are used to monitor wall cracks and their evolution. The base plates of our crack measurement tools are calibrated in millimeters. It also has a transparent top plate marked with a cross-shaped thin line cursor. Material: Acrylic colour: transparent Package Contents: 3 x crack measuring instrument Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.