PVC Backing Material:
Backer board is bonded to the back of the foam to add rigidity to the foam. This is helpful when storing Foam board vertically, mounting the foam vertically or for simply ensuring the foam lays flat on the table.
We use black PCV for our backer board because, like the foam, it is not effected by moisture and can be easily cleaned.
Black PVC backer board is 1/4".