Tombac pilgrim flask with screw-on lid and spout cover on Collections Sphere from

The ewer is unusual in that the cover for the mouth and the stopper for the spout are both screw-threaded, which allows them to be securely sealed in place. This implies that their purpose was more than keeping insects and the like away form the contents; rather, they were meant to minimize evaporation, a factor which has lead to the designation of such vessels as containers for Zamzam water. The somewhat flattened sides also allowed the ewer to be carried suspended from a saddle during the journey back from hajj.