What does H/HOZ mean in PCB manufacturing

In PCB manufacturing, H/HOZ is an abbreviation for how much copper thickness a prepreg or a core materials has attached to it.

H/H means half/half and OZ just means ounces.

In other words, H/HOZ means that there is half an ounce of copper foil (15.2μm) on each side of the prepreg or core material.

H/HOZ does not indicate a specific type of material, just the copper thickness on it.