A plastic or polymer material which can take many forms. In boats it is used, for example, to make moulded hoods for outboard motors, or the cases of some radios. For a boat-owner its more significant use is in fibrous form to make rope which is strong in relation to its cost – though not so strong as nylon or polyester in relation to diameter. Polypropylene ropes have the advantage that they float, whereas nylon and polyester do not. This makes them good for dinghy painters and ski-tows, but not for anchor rodes. However, it tends to become brittle and unreliable if exposed to sunlight since ultraviolet radiation from the sun seriously weakens it.