This bad boy will cover an all/glass aqueon overflow. It is too tall for a 75 but is darn near perfect for a 65/90 or 120 megaflow overflow. This is the only one I have at this size. It is just under 20" tall and 18" wide. It projects 10" into the tank including the overflow.
We put it in a 75 gallon tank at the LFS and it fits that dead space perfectly between the overflow and side wall. It is just too tall for the 75. A few inches would need to be trimmed as it would stick out above the water line. I really wish I would have brought my camera to take a pic. While talking to the owner we both thought it was almost the perfect aquacape for that half of the tank. It left 8" for a sand bed for an open look with maybe a small aquascape.
I will not be able to make another one this size. It didn't fit in any of my kilns. I had to pay a friend to fire it in his monster kiln. It was the only thing in the kiln. I can make them smaller but right now I will not be able to make one as detailed as this for a long time. I can do the hieght with minimal aquasculpting. Or short and beefy. But not tall and beefy.