Gator foam is a dense polyurethane foam board that can be squeezed without denting. Gator foam is not a common choice for backing board, as the rigidity is unnecessary for most framing projects, and
Actually, many artists paint on paper mounted to gator foam. Its lightweight characteristics are ideal for plein air paintings, and artists love it because it can easily be cut to size, whether 16x20, 11x14, or larger. Artists may fit 10 or more sheets of gator foam into their backpack, and it takes up hardly any weight.
If you ever need to make a sign that’s large and you don't want it to bow, use Gator foam. Common foam core can bow if it’s too large and not framed or behind glass. Gator foam, on the other hand, remains rigid, even when hanging on its own.