Samarium Cobalt magnets are the 2nd strongest type of magnet made. Nearly as strong as Neodymium, they have some pros and cons. They are generally expensive, they are brittle but they are quite powerful, they do not corrode like Neodymium magnets, and they can withstand high temperatures. These are surplus, we do not know the grade. Each magnet measures roughly 3/8 in x 7/16 in x 1/16, and they are marked on the North pole. They are also a bargain at this price and we have lots of them! These are especially useful in high temperature applications or in corrosive environments. $2.50 gets you 10 of these little guys.