Constructed at Hutt Workshops, the class utilised plate frames, partial mechanical lubrication, Franklin butterfly Firehole doors, and roller bearings on all but the trailing bogie. The class had a distinctive appearance when first outshopped, with a pressed smokebox front and the headlight jutting out forward of the top of the smokebox. This latter feature was soon changed at the insistence of one of the Railway’s Board of Management – instead, it was sunken flush into the smokebox, which required some modification and changed the aesthetic look of the class quite markedly.