The class consists of six heavy shunt U10B type locomotives built by General Electric United States at their Erie, Pennsylvania plant[2] in 1978.

[4] Originally an order for Philippine National Railways 2500 Class,[2] the six locomotives were purchased as by coincidence NZR needed a heavy shunter for Auckland container port transfer work.

They saw occasional service on the then under-used Auckland suburban passenger network where they performed well, but NZR focused them on their intended purpose, heavy shunting.

[4] The mill turned down the offer, instead, they purchased a DA class locomotive to perform shunting duties.

In July 1979 DH 905 was trialled at the Te Rapa marshalling yards in Hamilton, but the trial was unsuccessful and the locomotive returned to Auckland later that year.