CMS Magnetics Ceramic Magnets Hard Ferrite Magnets Ring shape D40mm - Crafts, Science and Hobbies

The ferrite magnet is not as powerful as neodymium magnets, ceramic magnets, or ferrite magnets are an economic solution for applications in which neodymium magnets are either too strong, too expensive, or environmental conditions are not ideal. Because of their extremely brittle nature, caution should be exercised when handling these magnets because they can expel shards if they are allowed to snap together or inadvertently slam against a magnetic surface. They are wonderful items for arts and crafts, school projects, fixtures, and closures.

Note:
All magnets are fragile and they may break or shatter. But if they are handled properly, they will last for a lifetime. 
Keep them away from pacemakers and children under 5 years old.