I ordered the SMALL size for my 8 lb. Maltese because it said "Up to 10 lbs." and I figured my 8 lb. Maltese would fit. Be aware that you need to measure your small dog's length to fit within this carrier in the SMALL size. The weight is not a good indication of the fit. The weight is confusing, so I bought a carrier too small for my dog. And the LARGE size "Up to 22 lbs" sounded too large, but might be ok.