Thanks for your interest at our shop and item.
We offer the size table at the bottom of the item's page, and you can find the "Cross section cm" at top of the size table.
So, the size of the item was marked by "cm", and it is not girth but "Cross section" of the item.
Please refer this when you choose the item.
Once again, thanks for your interest at our shop and item.
We will improve our service and try to offer the best to you.
Thanks a lot.