Necklaces are available in several sizes, knotted with leather strap for Dog or Cat. Repel Fleas and Ticks - Does not contain any harmful chemicals or ingredients. Sizing: Size shown in drop down is the smallest hole on the collar. There are 5 total holes .5" apart. For instance: 8" collar will fit 8", 8.75", 9.25", 10", 10.5" 12" collar will adjust for 12", 12.75", 13.25", 14", & 14.5" 22" collar will fit 22", 22.75", 23.25", 24", 24.5" 24" collar will adjust for 24", 24.75", 25.25", 25", & 26.5" Baltic Essential Amber Collars for Dogs and Cats -Natural Protection from Fleas and Ticks -All Natural from the earth, Organic, even safe to swallow – Completely from the earth.