 The uniting feature of the class was a top speed of and they all had two funnels.In 1913 the nine surviving "30 knotter" vessels with two funnels (all ten had been built by Thornycroft, but "Ariel" was lost before their renaming as D class) were retrospectively classified by the Admiralty as the D class to provide some system to the naming of HM destroyers.In the same way those with three funnels were classified as the C class and those with four funnels as the B class.