Neodymium Magnet in Steel Housing with Countersunk Hole 100 x 13 x 5 mm. 
 
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. It is much stronger than conventional ferrite magnets and generally has a protective coating because the material can corrode over time. The N indicates the magnetic grade, commonly ranging from N35 to N52. Higher numbers generally indicate greater magnetic attraction. The with Hole design for mechanical attachment, allowing screw mounting without adhesive.
 
This size provides substantial magnetic attraction and is suitable for strong attachments and robust projects. 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 medical devices and objects sensitive to magnetic fields, including cards and electronics.