Made with a shiny black plastic cap and a ferrite magnet in the bottom

math on blackboards (subtraction) etc

is standard for office magnets

Pack of 4 magnetic clips

Magnetark A4, Gult engros Made with a shiny blackA4 yellow magnetic foil. Magnetic sheets are not suitable for glass boards! High quality magnetic sheets. Cut it to the desired shape and size with regular scissors. Size: 21 cm x 30 cm (A4) Thickness: 1 mm. Strength: approx. 80 gr per sq. cm. Colour: strong yellow. Use it e. g. to make signs for the whiteboard or magnetic pieces for notes for the fridge. There are countless options. Magnetic sheets adhere to all magnetic surfaces, except glass