To find out if the harness fits comfortably for your dog, place two fingers under the harness at the neck and chest. If two fingers can fit, the harness is correctly adjusted. If two fingers can not fit and is too tight, please loosen the straps or opt for a larger size. If there is too much space, please adjust to tighten or opt for a smaller size.If by chance your pet tries to slide back out of the harness, please do not pull the leash