A bottle brush is a cleaning tool designed for scrubbing the insides of narrow-necked bottles, jars, and other containers. It typically features a long handle with a cluster of stiff bristles attached to the end, forming a cylindrical shape that fits into the interior of bottles. The bristles are usually made from synthetic materials like nylon or natural fibers, allowing them to effectively remove debris, grime, and residue from hard-to-reach areas. The handle can be made from various materials such as plastic, wood, or metal, and is often ergonomic for easy grip. Bottle brushes come in various sizes to accommodate different bottle shapes and sizes, and are commonly used for cleaning bottles, baby bottles, vases, thermos flasks, and more.