We purchased the Extra Small size it fit her at 6 lbs with room to spare. She must have been comfortable in them because she never tried to get them off.
Our 24 year old Maine coon cat was having problems making it to the box at night,& she slept with us. It was important to find pet diapers that would work. These diapers were the best product I have ever used. They were comfortable on her. She moved around in them with no problems and they never once leaked. “She put them to the test.” Best part I could easily remove the tabs to see if she needed a change. Super easy to use. They came with a nice premade hole for her tail that could be made larger if needed without compromising the fit. Last they came in a cute pink checkered pattern. She was our girl so it was a nice bonus. Compared with the pet stores these cat or small dog or rabbit diapers were cheaper and better quality and came in a 24 pack. Good price and great quality.