The Worsdell J class 4-2-2 was converted from compound to simple expansion working.

It is a 2-8-0 Consolidation of Southern's J class.

The J class also featured a number of other design advances over the K class.

The J class also featured substantially redesigned cylinder porting to improve steam flow and efficiency.

The endurance of the J class was considerably greater than previous submarines.

The submarine's layout differed from the other J class with the control room being placed behind the machinery spaces.

They should not be confused with the members of 1874's J class, the first tender locomotives to operate in New Zealand.

The retirement of the first J classes in 1900 left the designation available for reuse for these engines.

They should not be confused with the more famous J class of 1939.