Ruff Riders Roadie Canine Vehicle Safety and Training Harness - Size Medium1 Size MD1 fits dogs with a chest size from 28 to 30 inches and a maximum neck size of 20 to 22 inches Stress is placed on the chest instead of the neck of your dog The tether leash is adjustable and allows for movement Easy to use and can be left on all day in and out of the car Designed with input from a veterinary orthopedic surgeon and design engineer