I used this on an 18" round gas fire pit. I tried to get a round one but they were all either too big or too small. You do need some space around the fire pit to the tempered glass and this was just right. The square was just centered on the round fire pit. Worked out great. Assembly was pretty easy. A tip...I'm saving the box that it shipped in for winter storage as I won't be using our fire pit during the winter.