Possibly they meant 13-oz. banner material. More and more of these little league parks are going with banners.
We general only use 1/2" MDO because they take a beating from players running into them and balls denting them. We never use Sintra, Komatex or any of those products because of warping and if they don't take them in over the winter months, they'll generally crack. Cor-X is a No~No.
The thing I don't like about aluminum or the econolite/alumalite products is a person get hurt on them under the right conditions. They have very sharp corners and when reaching over or running along the warning path... you can really do some damage to an arm or eye if the player falls.