The Comfort Trainer size 6+ is for dogs over 150 lbs. Don't worry, the material is very strong, though light weight so that dogs do not feel pressure on their faces. The back strap is adjustable for a custom fit without facial irritation. The Comfort Trainer was designed to be worn looser than other head collars, offering your dog the ability to catch a ball in the air should they want to. This non-binding training tool will help you gently redirect your dog, when needed.