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. Made in Japan by Marna.