Here's my teapot, a bit on the small side, but the handle is quite big. However, it fits really well.
This is a larger tea pot that the one above. I tried the cosy on it and with the spout and handle in the pointed areas, it fitted quite well too. I would suggest that a 9" or 10" square would work better for this size of teapot.I tried the cosy on it with the spout and handle in the pointed areas, it fitted quite well. I would suggest that a 9" or 10" square would work better for this size of tea pot.