[For small dogs, medium dogs and cats] The length of the Airtag dog collar is 21.3 inches, but with the multiple holes on the strap, you can adjust it from 9 to 19.5 inches to fit your pets. We recommend using it on cats, small dogs and medium dogs. [How to Assemble] Measure around the base of your pet’s neck, keeping one finger between their neck and the tape. Cut the extra tape to fit your pet’s neck. [Compatible with Apple Airtag] Airtag dog and cat collar is fully compatible with Apple Airtags. By using this tag collar, you can keep track of your cats and dogs when they are hiding somewhere in the house. Never lose your pets with this small airtag dog/cat collar. [Comfortable and Durable] This airtag dog and cat collar is made of soft silicone, which is non-toxic, comfortable, sweat-proof, scratch-resistant and washable. 43g light weight, easy to carry. Please note that it is not suitable for small and skinny cats.