A bottle is a rigid container with a neck that is narrower than the body and a "mouth". By contrast, a jar or jug has a relatively large mouth or opening which may be as wide as the overall container. Bottles are often made of glass, clay, plastic, aluminium or other impervious materials, and typically used to store liquids such as water, milk, soft drinks, beer, wine, cooking oil, medicine, shampoo, ink, and chemicals. A device applied in the bottling line to seal the mouth of a bottle is termed an external bottle cap, closure, or internal stopper. A bottle can also be sealed by a conductive "innerseal" by using induction sealing.