Product review (2 stars): Price low=CHEAP!
I guess I should have guessed as much based on the price paid, but you could easily cut out your own foil and have the same effect.  These are thin and crease easily under the weight of the steel grate on top of it.  I've decided to change once a week (because really they won't last more than that, unless you don't cook at all) and look for something more sturdy in the future.