They are constructed from durable, UV resistant ABS plastic and are designed with non-skid surface, all these make them suitable for extended external use. They have detachable cover so that you can completely remove it, their opening is easy, since the specially designed thread automatically ejects the cover, once you turn it 90o anticlockwise. In that way someone can achieve the access and control of various areas of a boat. The Watertight Plugs EVAL feature an O-ring seal that makes them watertight and are mounted with hidden screws for discrete appearance.