[For Small Dogs, Medium Dogs and Cats] The length of the airtag dog collar is 21.3inches, but with the multiple holes on the strap, you can adjust it from 9-19.5inch to fit your pets. We would recommend you to use it on cats, small dogs, and medium dogs. [How to assemble] Measure around the base of your pet's neck, keeping one finger between its neck and the tape. Cut the extra tape to fit your pet's neck. [Compatible with Apple Airtag] Airtag dog cat collar is totally compatible with Apple Airtags. By using this airtag holder collar, you can keep track of your cats and dogs when they are hiding somewhere in the house. Never lose your pets with this little airtag dog/cat collar. [Comfortable and Durable] This airtag dog cat collar is made of soft silicone, which is nontoxic, comfortable, sweat-proof, scratch-resistant, and washable. Light weight of 43g, easy to carry on. Please note, it is not fit for small and skinny cat.