Our hospital had a couple of them floating around each room and they were all different sizes...Im 5'1 and have a 55 cm on at home and my hips are still above my knees when Im on it, and I use it all the time.... a much larger one for me feels like Im going to fall off and I cant actually sit on top but rather near the side if that makes sense! Maybe check with your hospital and see if they have different sized ones?