Extensively tested to ensure it fits into the popular narrow-necked reusable water bottles. In fact, it is the only natural fiber brush that fits these bottles. The 100% natural coconut fiber bristles are long and flexible, allowing them to compress to fit through the narrow neck and to spring back out ready to clean right into those hard-to-reach corners. This brush is ideal for your reusable water bottles, baby bottles, wine glasses, vases and jars. Ethically handmade from 100% natural, sustainable coconut fibers, this bottle brush won’t become smelly or moldy with use.