A dog harness is recommended for almost all dogs if you want to keep your dog safe while walking. The dog harness can even be attached to a muzzle, so you can avoid having to remove the muzzle.
However, our harness sizes do not cover all dog breeds, for e.g. extra large dogs like the Newfoundland or extra small dogs like the Chihuahua are so big/small, that they should be collared instead.