My puppy is still nervous about this harness - particularly if I want to leave him in the car (only for a few minutes). He's getting better about it, but when he gets nervous he can back himself out of this harness. I'm certain that the harness fits properly - if anything it's too tight not too loose. But the next size is still WAY too big.I tried to contact the company who makes this harness about the problem. I got a reply that sounded as if it's my puppy's problem - not a product problem and that the designer would need to contact me. The designer never contacted me.Regardless, the intent of the harness is to secure the dog to the vehicle in case of an accident. I would imagine ALL dogs will be scared if in an accident and are likely to attempt to get loose. This harness seems to allow that outcome.