Neodymium Block Magnet with Countersunk Hole 40 x 20 x 5 mm N48. 
 
A neodymium magnet (NdFeB) is very strong. It is magnetised in a strong magnetic field during manufacture, providing high magnetic attraction in a compact size. Compared with ferrite, neodymium provides much greater magnetic attraction. A protective surface coating helps improve durability. N48 indicates the magnetic grade. NdFeB grades commonly range from N35 to N52, with higher numbers generally indicating stronger magnets. The with Hole design for mechanical attachment, allowing screw mounting without adhesive.
 
The 40×20×5 mm block is suitable where a substantial but manageable hold is needed in workshops. For good results, use a flat, clean metal surface. Any gap caused by thick paint or an uneven surface reduces holding force. Do not overtighten the screw when securing the magnet. Neodymium can break under impact or pressure. Use a washer or spacer if necessary.
 
Warning: not suitable for children. Two magnets can snap together quickly, pinch fingers and crack or chip. Separate them carefully and avoid impacts. Keep them away from bank cards, sensitive electronics and medical devices.