Description:OOTDTY Features: This item is easy to use. Just place the card on the surface of the magnetic material and it will reveal a magnetic field of pattern. Great for personal or scientific research. And it help us study magnetic fields that we can't see. It can be used for quality control, product demonstration, reverse engineering, authentication and educational purposes. Compact and portable size, lightweight, convenient to carry with you. Wonderful educational tool to stimulate our interest in science. Magnetic field viewer is a micro-encapsulated film which makes user view a static magnetic field. The highly flexible film suit for magnetic surfaces with any degree of convexity or concavity. Specification:Dimensions: 50x50mm(1.97x1.97in)(approx)Color: Dark GreenQuantity: 1 pcNote:Transition: 1cm=10mm=0.39inchNo retail package. Please allow 1-3mm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package includes:1 x Magnetic Field Viewer(other accessories demo in the picture is not included.)