The requirements were for larger water and coal capacity on a locomotive that could handle grades better than the F class.

The locomotives were re-equipped with Walschaerts valve motion, new side tanks and cabs, and a larger boiler.

[1] FA 9 also differed from the standard rebuilds in that its trailing truck had outside journal boxes instead of the internal type used on the other engines.

[n 1] The remains of the locomotives, if they still exist, comprise the frames, cowcatchers, cylinders, upper cab and coal bunkers.

The last in service, FA 251, was displaced permanently in 1947 by the arrival of the railway's second Drewry 0-6-0DM diesel locomotive.

These two engines were later displaced by two Drewry 0-6-0DM diesel locomotives, and FA 41 was onsold to Auckland Farmers Freezing Company (AFFCo) in 1960.

When the former FA 41 was withdrawn in 1980, its frame was donated to the Bush Tramway Club at Pukemiro Junction for spare parts.