Wendsy: As I undestand it, your centre can measure anything from 12.5" to 24.5" edge to edge. If this is the case, then 21"edge to edge qualifies. I haven't even measured mine yet, but I think it will be about 22"edge to edge, when I'm finished with it. I would have no proble if it's a little short, whoever is doing the first border, could show a heap of creativity.