It is small but I think it depends on how your baby is built, some dogs weigh 3 lbs but have longer legs and are just takker and skinnier, and some can be the same weight or more and be smaller like my baby. He is about 3.6 lbs and I thought the small would be too small but he still has room inside. I think it can go up to 3 1/2 or 4 lbs. |