tlambing, it's always been very flexible. I would estimate, 12 1/2" sq to 20-24" sq. Or, it can be oblong also. I really think it's up to the maker. Is that right girls (guys)? It's been a long time since I've been in the swap. Have the rules changed? I guess that's a good thing to know now, before I send the wrong size one. (There is time to make another if I need to.)