4x2 mm N52 Neodymium Disc Magnet. Neodymium is about as common as tin or lead. There are two types of “Rare Earth Magnets” SMCO (Samarium-Cobalt) and Neodymium. Neodymium are the magnetically stronger and cheaper of the two but are more susceptible to oxidation, this is why they are protected by Nickel plating.
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