These suctions cups will stick on any smooth, non-porous surface. Use them in the office to hang ID card, keys or signs. At home they're handy for hanging eyeglasses, toys or awards, or even in the shower to hang your loofa! Teachers find them handy in the classroom for displaying artwork. You can also use them to hang documents, safety goggles and other items. Each hooked suction cup is 1 5/8 inches in diameter.