Features: 1.Device for measuring the changes in distances between points in solid bodies that occur when the body is deformed. 2.It is used either to obtain information from which stresses (internal forces) in bodies can be calculated or to act as indicating elements on devices for measuring such quantities as force,pressure,and acceleration. 3.Suitable for all transparent lens and coloured lens. Specifications: Structure: as described Item name: Lens stress detector Electric Voltage: 220V/50Hz Power: 15W Volume: 11.5 x 8 x 13cm Plug Type: EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on. color: White material: plastic Package Contents: 2 x Lens Stress Detector Tester 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.