Adjustable Pet Dog Collar Light Up 7 Colors Sizes S-XL Use 2 CR2032 batteries. Individually packaged: yes Unit Weight: 4 oz. S: width 1", length can be adjusted from 12"-14" (2" adjustable range) LED length 8" M: width 1", length can be adjusted from 14"-19" (5" adjustable range) LED length 9" L: width 1", length can be adjusted from 15"-22" (7" adjustable range) LED length 10" XL: width 1", length can be adjusted from 16"-24" (8" adjustable range) LED length 10.5"