Tray for Planters 17-24" Charcoal Gray

Is because even though it's sturdy, flexible, passable and looks OK my biggest issue is the center, even though it can hold multiple different sizes. The center of it has a lifted area rather than flat. Which I'm assuming is used for smaller pots but once you go bigger, like let's say hypothetically, you buy a pot that's wider and taller, but gets thinner as you go through the center. The pot may be balancing itself on the circular center, even though it's taller and wider. I still kept them and use them for bigger pots to where I can set them completely on top and not worry about it, however, for the pots I described that are wider, but start getting smaller in the base, I didn't want to run the risk of wobble (which I had). I simply just retrofitted on a taller, wider pot, but I felt that it was very limiting because it's meant to be for multiple types of pots. but has issues with pots that are bigger, wider, taller, but thinner at the base like an inverted triangle.