This is a great training tool for that stubborn dog. Copper rivets are mounted to the inside of this collar to control your dog. Collar is fitted on dog and cinches when pulled on. Sized from end of buckle to the end of collar. 1-1/4" Wide. For correct collar size, measure your dogs neck & add 4 to 5 inches. In sizes 19, 21, 23, 25 & 27.