Made of premium quality foam material and high density felt bottom, non-toxic, only the back side with high density felt bottom is magnetic.^ Designed in a square size 5 x 5 x 2 cm (1.97 x 1.9 x 0.79 inch), the eraser features small, lightweight, suitable for children and adults.^ A good assistant with strong absorb-ability, they are not just erasers, but also can be used as magnets on whiteboard or any other magnetic surface, a handy necessary for classroom, school, home, office meeting.^ To clean the whiteboard easily and effectively, just swipe the eraser with a little pressure to clean your whiteboard.^ Package: includes 40 pieces magnetic whiteboard erasers in 4 colors, 10 pieces for each color.