Dog Training Collar This is Extra Large Size Collar Chrome plated steel wire, adjustable length, Heavy duty links for strength and durability Collar wire size: 4.00 mm Collar (interior) circumference is approximately 23.5" There are nine links, eight links are removeable Could be added or reduced some link to fit your dog's size,Each link size approximately : 1.25"W x 1.25"H x 1.95"L To determine the proper size, measure the circumference of pets neck and add 2"