An ingenious and effortless way to clean the inside of bottles and other containers with narrow openings. These bean-shaped sponges contain alumina ceramic balls inside, which add a heft--allowing for a truly impressive kind of clean. Simply insert the sponges, a little water, and a drop of soap; then cover and shake away. It's really that easy. String can be tied to sponge at hole on top to enable pulling dropped sponge through extra narrow openings.