They were unusual for their time, with a wheel arrangement of 0-4-2. This arrangement was used by few of the other railway companies, and never proved popular (although the Great Northern Railway had 150 such locomotives).
These locomotives were distinctive for their unique wheel arrangement of 0-4-2, which was uncommon among other rail companies.  While this configuration was used by a few others, it did not become widely adopted. The Great Northern Railway had the most notable use of these locomotives with 150 units in service.