Features: brand new and high quality High Quality Material: Made of high quality magnet. 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'for t see. Application: Good performance, convenient and practical, suitable for home and professional use. Lightweight Size: Portable and small size, easy to store and carry, bring you convenience. Specifications: Material: Magnet Color: Green Type: A, B, C Product Dimension: approx. 25x35mm/0.98x1.38inches 40x45mm/1.57x1.77inches 30x50mm/1.18x1.97inches Net Weight: 10g/0.02lbs 20g/0.04lbs 25g/0.06lbs Package Includes: 1x Magnetic Field Viewer Viewing Film note: Please allow 1-2cm errors due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item.