The Lewis gun, which weighed 27 lb (12.3 kg), was commonly used with a 47-round drum and bipod; it was used on the move in support of squads, and on vehicles and aircraft as well, or on a tripod (either for anti-aircraft use, or to fill in for a heavier MG). What made it very useful was that it was significantly lighter than water-cooled weapons, but could fire nearly as much due to a very large cooling assembly. These sort of multi-purpose machine guns, would be further developed, and later given names like Universal Machine gun or general-purpose machine gun, and would eventually supplant the water-cooled designs. Later designs have mostly switched to fast barrel-replacement as an alternative to cooling, which further reduces the weapon's weight (but can increase the total weight carried by a soldier). Some earlier designs, like the Vickers, provided for the replacement of worn barrels. It was in the 1920s and 1930s that barrel replacement as a means of cooling became more popular (e.g., in the ZB 1930, and later the MG34 and the Bren gun).