The disposable or single-use camera is a simple box camera sold with a roll of film installed, meant to be used once. Most use focus free lenses. Some are equipped with an integrated flash unit, and there are even water proof versions for underwater photography. Internally, the cameras use a 135 film or an APS cartridge. The whole camera is handed in for processing. Some of the cameras are recycled, i.e. refilled with film and resold. "Disposable" digital cameras are a recent innovation. These types of cameras forego film and use digital technology to take pictures, and the cameras are returned for processing in the same fashion as film cameras.