I'm a bottle cap collector, these magnets are just the right size for the interior/bottom of a cap (diameter and depth). Maybe a little strong for the purpose of holding up a single cap but I didn't want to have to glue or "build up" the depth and use a weaker/thinner magnet. For folks who plan to use these with crafts (fridge magnet type deals) these are plenty strong enough to hold any photo or school lunch menu on the fridge plus some.