To provide services over the extension, the CLR ordered 24 additional driving motor carriages from the Brush Company, which, when delivered in 1917, were first borrowed by the Baker Street and Waterloo Railway for use in place of carriages ordered for its extension to Watford Junction. The new carriages were the first for tube-sized trains that were fully enclosed, without gated platforms at the rear, and were provided with hinged doors in the sides to speed-up passenger loading times. To operate with the new stock the CLR converted 48 existing carriages, providing a total of 72 carriages for twelve six-car trains. Modifications made while in use on the Watford extension meant that the new carriages were not compatible with the rest of the CLR's fleet and they became known as the "Ealing stock".