 The most important difference was that the Admiralty R class had two shafts and geared turbines, compared with the three shafts and direct turbines of the Admiralty M class, but in appearance the R class could be distinguished from its predecessors by having the after 4-inch gun mounted in a bandstand.The Admiralty ordered the first two of this class of ships in May 1915.Another seventeen were ordered in July 1915, a further eight in December 1915, and a final twenty-three in March 1916 (of which eleven were to a slightly modified design).