I decided to spend a little more on a harness after not being able to find one that would actually fit my little dog that she could not wiggle out of. And, paying that extra money has paid off! Finally! My little Birdie is 10 pounds and the XXS fits her perfectly. She is full grown so I'm looking forward to this harness serving us for a long time. Thankful for the extra strap that keeps her extra secure. It is so lightweight, also. I live in Arizona, so having something breathable is key to her staying cool in the summer months.