*Medium: 11-27kgs. Cocker Spaniels, Dalmations, Hounds
*Large: 27-59kgs. Labradors, Collies, Shepherds
*X-Large: 59 kgs. Mastifs and Oversized Dogs
I noticed an immediate difference using this style of halter. I've tried others, and this one is by the best, the nose strap doesn't seem to bother the dogs as much or inhibit their gait like other harnesses.