Features: for Ideal for metal recyclers, brokers, antique buyers, collectors, or anyone that needs a convenient, easy-to-carry magnet to test for iron, nickel, or cobalt content. Identify fake/plated jewelry, which often has steel or nickel alloys as the base material (some alloys, like nickel-silver and German silver are non-magnet, despite having ferrous metals present). Generally, the magnet test is only the first test performed, before density and acid testing. Identify/sort chrome plated items from polished aluminum, silver, and non-magnet grades of stainless steel (chrome plating requires a nickel layer, which is magnet). Identify and sort solid brass and bronze from steel-plated items (handy in the antique market and hardware store). Package Includes: 1 Piece Keyring Specifications: Material: Iron Size: Base 1: Approx.12mm/0.47inch (maximum Pull-off Force 4kg) Base 2: Approx.15mm/0.59inch (maximum Pull-off Force 9kg) Base 3: Approx.17mm/0.66inch (maximum Pull-off Force 13.5kg) Base 4: Approx.21mm/0.82inch (maximum Pull-off Force 17kg) Iron for Shell Plating: Nickel Copper Nickel Adsorption Direction: Only the Bottom is Magnet Use Temperature: Not Higher Than 75 Degrees note: Please allow 1-2cm errors due to manual measurement,pls make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.