Gauge (pipe and tubing)
In North America, gauge can also be used to describe the pipe or tubing that is used to construct many kinds of metal fencing.
In this case, gauge is equivalent to wall thickness, and as with wire, the lower the number, the thicker the wall of pipe and tubing is.
Most chain link fencing in North America doesn't use anything smaller than 17 gauge, but there are other types of fence panels and systems that use thinner gauge material.
It's important that you always compare not only the outside diameter or OD of the tubing you've been quoted for your fence, but also the gauge. Heavier duty pipe and tubing will always be stronger and more durable.