These are small earth magnets . Composed of Neodymium/Iron/Boron (NdFeB), these magnets are strong and make for a great way to attach tools to a metal workbench, hold small children to a fridge, and as a trigger for reed switches. 

Features

• Diameter : 20 x 9.4 x 2.5 mm 
• Thickness : 3.2 mm
• Material: NdFeB
• Grade : N42
• Plating/Coating: Ni-Cu-Ni (Nickel)
• Magnetization Direction: Axial (Poles on Flat Ends)