The sample is a countersunk hole square magnet, it is made of rare earth neodymium. The magnet is plated black epoxy to keep away corrosion and oxidation, because neodymium material is easy to corrision and oxidation. This is a high cost performance material so that be chose by many custom. The grade is N52, youcan also choose N35/N38/N40/N42/N45/N48/N50. The number is higher, the greater is performance, but the price is also higher.
It can be used in many places, such as gluing on the back of projects that require extreme strength in small sizes (suitable for homes, schools, offices and shops), it also can use in permanent magnet motor motor, automotive industry, audio-visual equipment, IT information, medical equipment, mining equipment, industrial automation, sports equipment, electrical appliances, clocks, LED lighting, security equipment, hardware and plastics and other fields.
It should be noted that these magnets are not suitable for use by children, neodymium magnet has strong power and easy to pinch one's hand.
More introductions;
What is a square countersunk hole magnets? Types and benefits