smidgen uses mine happily. Esther doesn't. But then the corner one has a door on it and the other one doesn't so not sure if the door is the impediment to use, or the shape. But as I said, Smidge is perfectly happy with his (as am I, because of space issues). Also, Misty had a corner one, and she (a British Short Hair) used it happily. She was a biiiiiiiiiiig cat, so clearly there is room to manoeuvre....