Bottle Cleaning Balls, set of 3, silicone with stainless steel core. These super-cleaning bottle balls get into areas where bottle brushes can't go. Use them to clean water bottles, decanters, baby bottles, vases and more. The weighted stainless steel core, surrounded by soft-scrubbing silicone bristles, forces the scrubber against surfaces when you shake the container. Bacteria and odour resistant.