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 . You can use our corner crack monitor to monitor the horizontal or vertical movement of cracks on a flat surface . It is a . Tell the story of 2D manual crack monitoring work . Crack monitors are used to monitor wall cracks and their . The base plates of our crack measurement tools are calibrated in millimeters . It also has a transparent top plate marked with a -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 .