The driving wheel diameter was 1,092 millimetres (3 ft 7.0 in) and the tender has two axles. The valve gear is an Allan type with Saltersafety valves on a domed boiler. It originally had a rapid ejection (pop) safety valves and the locomotive itself had no brakes, those being only on the tender.
This class was little changed compared to the 2-4-0 tank locomotive imported at the same time, aside from having brakes on the locomotive body and an improved safety valve. Some engines were given larger cylinders.