Neodymium magnet with 20mm Outer Diameter,4mm Internal Diameter, 9mm CSK (Countersunk)diameter, 3mm Thickness, Disc shaped, Color and plating: Nickel, Temperature tolerance: 80 degree C ,Set of 5pcs.WARNING AND SAFETY PRECAUTION – Do not bring a magnet near a person having pace maker or electrical medical device. – Magnets have strong power of attraction. – The brittle nature of the magnet can lead to flying chips if the magnets are allowed to impact each other or a solid surface. – Do not swallow or store in moist environment. – Magnetic properties drop when heated. – Do not place magnets near electronic devices and magnetic storage device like prepaid card, floppy disc, television, etc. – Larger magnets can become a pinching hazard if caution is not exercised. – Usage of protective gloves and eyewear while handling larger magnets is highly recommended.