From powerful permanent magnets toward little ones almost without available force, this area has developed different methods to identify which one is stronger. The most used classification for neodymium magnets starts with an “N” taken from its name and a two digit number, normally from 24 to 52 with a theoretical limit of 64.
In some circumstances they also employ a suffix useful to know the maximum temperature that the magnet resists without losing output quality.
Neodymium is called a rare earth metal but not for being singularly scarce in the planet. It's in relationship with the dispersed state in which rare earth elements are found. It's ahead of other magnets like SmCo, alnico or ceramic. They are used in hard drives, guitar pickups, electric engines, loudspeakers, medical devices, ...
Not too many problems to find N50 and N52 in certain sizes, and they have a surprising force. Furthermore this kind of magnets are potentially dangerous and must be handled with precaution. An example: a small N52 magnet with one inch (2.54 cm) of diameter and height has a pulling force of more than fifty kilograms!