Plastic magnet is powerful neodymium magnet enclosed in a durable plastic housing. As the magnet’s nickle plating is completely covered by plastic cover, these magnets are safe to use in harsh environments especially does well in the underwater application, also the magnet is very durable and will not chip or break from usage.
The plastic coating is about 1mm thick itself, according to the final size, the magnet size should change to be 2mm less. But it will make the magnet less stronger, if you choose plastic coating, you may have to choose a stronger magnet than your original design. In addition, the plastic coating will need a tooling charge, but different colors can be produced by a same mold.