These fun little sticks are actually the branches of the Silver vine bush! We bind three sticks with natural fiber twine in each order. In the very center of the stick you can see a very slight color change from the pulp of the stick. That is the good stuff cats crave! The best part of these very inexpensive "toys" are that they help to clean the nasty tartar off of their teeth! Cats and poor dental hygiene is a nightmare. Dental work at a vet is traumatizing for a cat and VERY EXPENSIVE! Cats will get a nice thumbs up from the dentist after chewing on these guys, not to mention a nice little buzz. If your kitty is kind of "eh" about the sticks, you can strip a bit off of the bark to freshen up the Silvervine aroma and make it attractive again. No kitten zone. At approx. 1 year of age, instincts should kick in and they will spit out any pieces of bark too big to swallow.