All they'll need is their own craft supplies and embellishments to make unique and one-of-a-kind Christmas bulb ornaments. They can open up the ball ornament to place glitter and photos inside, or they can just decorate the outside. No matter how they choose to decorate, they'll have a Christmas ornament to cherish for years to come. Plastic. (2 dozen per unit) 2 1/2" x 1" The back is not flat.