This is a N35 Neodymium (also known as NdFeb, NIB, or Noe) disc magnet of dimension 10mm x 5mm. Neodymium magnet. This magnet is suitable for DIY projects, such as whiteboard fixing, adsorption of various steel parts, etc.
A neodymium magnet is made from an alloy of neodymium, iron, and boron. They have excellent magnetic properties and are extremely strong for their small size. These magnets are permanent and have a high maximum magnetic energy.