Aluminum foil.Made of premium quality materials, nontoxic and safe for use.PERFECT FOR MANY OCCASIONS whether you have got a classroom Valentine's Day party, a classroom Valentine's Day celebration, a beautiful wedding, or a special heart warming home event to decorate, add a pop of soft pink to any venue with our decorations!We monitor our balloons in the production process so they have a much higher latex content than the industry standard which means they are lightweight and have an impressive durability that won't pop unless you want them to!