Engage in magnet play, build pyramids, count, sort, and more! Includes 20 magnet marbles (.63 inch in diameter each) in solid colors (assorted) in a clear dish with a lid. Ceramic magnets are encased in plastic completely. Ceramic magnets are the most lightweight and economical magnets. Usage tips: Avoid dropping or banging. Although they are more durable when encased in plastic (as this product is), ceramic magnets that have been dropped or impacted by force can break or chip. That is a property of the ceramic material. Also, any magnet that is dropped or banged can lose its magnetism--its domains inside can get misaligned. Storage: Store all magnets away from high heat and direct sunlight. Child safety tested for ages 4+/grades preK+.