IDEAL FOR PROVIDING ROTATIONAL MOVEMENT. Unusually, diametrically magnetised magnets are not designed to hold the maximum possible weight for the size of the magnet but instead are used to provide rotational movement. CORROSION-RESISTANT PREMIUM COATING. Coated with three layers of nickel, copper, and nickel to reduce corrosion and provide a smooth and clean finish. RESISTANT TO DEMAGNETISATION. Excellent resistance to demagnetisation. SPECIFICATIONS. 20mm diameter x 20mm thick with a 6mm central hole.