The JAF class was built in late 1977. They were gravity discharge hoppers for the transport of soda ash used in the manufacture of glass. They were unloaded at the ICI glass plant at Yarraville.
The wagons were numbered 501 - 510. The class was going to be 'JAX' but intersystem operations caused the final designation to be 'JAF'.
In the 1979 recoding the class became VHAY.
The class was relettered from JAF between 1979 and 1981.
In 1987/1988, the most of the class was relettered to VHAF when the letter 'Y' was dropped from the coding system.
The last VHAY in service was VHAY 507. This was modified and reclassed to VHFX in about 1991.
VHAF 505, 506, 509 were modified and and reclassed to VHFX in 1991.
VHAF 50 - 504, 508, 510 were modified and reclassed to VHFF during 1993.
Modifications to both classes enabled the wagons to carry either cement or fertiliser.