Cool learning tool: Magnetic viewing film are great for interpreting magnetic fields and seeing how they interact and can change weaker magnetic fields and other little things that really show what's going on with those forces when it's not an force very much Helpful How to use: Put the magnetic pattern detector on the of the magnetic or magnetized object, observe the range and strength of the magnetic field, try to get close to the object to be tested or tear off the film to be tested for detection. Improve sensitivity Maintenance Tips: The magnet pattern detector is surrounded by a black paper photo frame, please place it in a dry and ventilated place to avoid prolonged exposure to sunlight and dark and humid environments Spot magnets in objects: This is a fun way to spot magnets in objects by using a magnet pattern detector, a magnetic clasp on a laptop, a speaker on a cell phone, or a door seal on a refrigerator What you get: 4 x 4 inch magnetic viewing film included in the package, surrounded by a black paper photo frame, edge seals help prolong life color:As shown Material:composite material size:100 x 100mm Package Contents: 4 x magnetic viewing film 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.