These mats work great for about a week (approx 10 projects). In fact, sometimes too good. Then, all of a sudden, the corners seem to loose their adhesiveness. I have to keep masking tape handy so I can secure the corners. Also, I've noticed that they don't last at all if I use Brazzil paper or others that say they're cardstock but have a very high fiber content, much like construction paper. Once I even received a \"new\" mat that the clear cover didn't stick to. Wish there was a happy medium.