Unless you’re making an exotic PCB, your conducting material will be copper. When fabricating a copper conductor PCB, the only real flexibility you get is in the thickness of the copper which is often referred to as copper weight. Most fabricators offer a range of options from 0.5 to 4 ounces. For reference, 1 ounce (oz) copper is approximately 1.4 mils thick. Single ounce copper also happens to be the most frequently utilized thickness for outer PCB layers and 0.5 oz copper is the most common option for internal layers.