The neck ring DEFINITELY affects mobility to a significant degree. When I first tried the Fusion dry suit, I went out in my doubles and did a valve drill and ended up doubled over, giggling, because it was so darned trivial. Once I installed the neck ring on my suit, reaching the isolator became sufficiently difficult that I actually had to change undergarments to gain enough reach to get it. It was a great disappointment, since the mobility was one of the biggest selling points of the suit for me. However, I kill neck seals, getting only about six months from one, so sending a suit in every six months for repair wasn't an attractive option, either. My Santi suit, which does NOT have the neck ring, has already been back for seals, and it's only a little over six months old.