N52 and N55

Neodymium magnets can be made of several materials, which are designated by the letter N and a two-digit number.  The most commonly used materials are N35, N38, N42, N45, N50 and N52. The larger the number following the letter N, the stronger the magnet. N55 and N52 are currently the strongest magnetic materials in the world. They are mainly used when you are limited by space (the magnet needs to be small) and you need to achieve the greatest magnetic force. If you are not limited by space, you can also achieve greater magnetic strength by using a larger magnet.