You'll need 2, Meredith; they are adjustable, but not that much. There are 6 different sizes, you need to measure the chest circumference (it shows where on the GL website) Jack's was too big for him when I first got it ( he weighed 64# then). Now that he's up to 80#, I've adjusted it, and it fits fine, but one size won't work from puppyhood through to a standard adult. I'd get one for now & wait 'til he outgrows it to get the next one.
I'm thinking of trying either the head collar or the harness and I read all the comments...hoping someone else had asked my question. Can you leave either one on them all the time, like you would a collar....or would you only put it on if they are going on the leash? If you only use it when on the leash....does the dog wear a normal collar, too?
Tricia, the harness only goes on when you are taking the dog somewhere on leash... you should never leave either one on all the time, it would be very uncomfortable for the dog, ( especially the head collar!), and would be a potential hazard if the harness caught on something.
Jackdoodle wears his plain flat nylon buckle collar all the time, and the harness goes on when we leave the house.