It fits the baking sheet perfectly. I’m updating my review to share that I absolutely love this product. It’s been absolutely wonderful to bake things on and it makes clean up a breeze. Unfortunately, my husband got a little overzealous and used a pizza cutter on it yesterday. He was surprised, given that our pizza cutter blade isn’t exactly sharp. But it now has some interesting angular cut marks. The sheet still works but we will be ordering a new one.