I bought them with the grill. I cut one into 1/3 and 2/3, so I have 3 different pieces. The uncut one almost covers the entire surface of the grill I have. I use the cut pieces depending on whether I want to grill 2 steaks and a lot of vegetables, or many steaks and few vegetables (for example, the other day I grilled onions sliced into rings). Anyway, I put the membrane on when the grill has already heated up, and it warms up directly, and I have grilled many times without any problem. It cleans very easily.