[Premium Acrylic Material]This crack monitoring record is made of high quality acrylic material, which is sturdy and can be used repeatedly. It is waterproof, sunproof, wear-resistant and scratch-resistant. It is easy to install and intuitive to read. []Our crack monitor gauge adopts advanced technology, perfect for tracking horizontal and vertical crack motion on flat surfaces. This can reliable detection and monitoring of changes in crack width or length over time. [Purpose]This Crack monitor gauge is designed to monitor cracks in walls and how they over time. The instrument consists of a scale plate and an indicator plate, scale plate (with scales in both horizontal and vertical directions), and indicator plate (one or two crossed indicator lines). [Widely Uses]Our crack measure and record instrument is widely used for observing the opening and closing of cracks and misalignment on the of various buildings. It can also monitor the relative displacement between two points in the horizontal and vertical directions. Parts List: 3 Pairs of Crack Monitoring Record 12xScrews 3xMonitors Our crack monitoring record is designed to monitor cracks in walls and how they over time. It is made of acrylic material, which is waterproof and sun-proof. It is reliable to monitor and easy to read. Feature: Waterproof Device: This crack monitoring record is waterproof and easy to install. It can be used for monitoring of changes in crack width or length over time. Reliable to Use: This crack monitor gauge can be used for observing the opening and closing of cracks and misalignment on the of various buildings. It is reliable to operate. Specification: Product Name: Crack Monitoring Record Measuring range: -30 - +30 mm Resolution: 1 mm Measurement accuracy: 1 mm Ruler size: 100x30 mm Purpose: Can be used to monitor wall deformation/cracks Material: Acrylic Color: As Shown Package Contents: 1set * Crack Monitoring Record Notes: 1.There may be slight differences between the picture and the actual color of the commodity. We will try our best to show you the exact color. 2.Please allow slight dimension difference due to manual measurement. 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.