Magnetic Marbles - Pack of 20 Immediate dispatch, estimated delivery date in around 10 working days - not the longer Amazon ETA These plastic cased marbles look like colourful plastic balls, but each one contains a magnet so they stick together, hang together and pull towards and away from each other. As a first introduction to the magical world of magnetism they are great fun. Ideal for use with magnetic wands. Because of the magnetic element to these marbles, they are NOT suitable for children under 6 years of age.. Pack contains 20 x marbles. Diameter of marble - 17mm