I originally bought a Large for my 12YO Lab to help him walk - that was BEFORE his cancer amputation. I don't use a vest for him anymore... BUT, I just adopted a three-legged Lab puppy and he can wiggle his way out of ANYTHING except this! It has that third strap around his tummy that keeps it on him... SO I've now ordered a small size for him - got tired of cinching the size large to make it fit.This vest ROCKS! BUY IT!
Our Heinz 57 puppy was able to wiggle out of any harness and collar we put on her. This fits great and she hasn't been able to wiggle out. This is a great harness for the dog that has a secret identity as an escape artist! My baby is a 40 pound whippet/Shepard mix and the small fit her great.