Each package comes with a Buddy Tag and a color matching Silicone Wristband as a complete set. The Silicone wristband is comfortable and adjustable to fit most children's wrist size (the wristband is 7? long) and some of younger children’s ankles. The mobile app is FREE and there are no monthly fees. Buddy Tag and its app are compatible with iPhones running iOS 9 and above and Android devices using Android version 4.3 (Jelly Bean) and above. The backside of each Silicone wristband includes a white strip for personal ID that can be added with a regular pen or a Sharpie. The custom designed coin screw closure secures the Silicone wristband on your child’s wrist to prevent easy removal. Each Buddy Tag wristband is custom designed to fit the Buddy Tag. Buddy Tag is waterproof, and it can be used for water safety alert to help prevent accidental drowning. The Buddy Tag can be removed from the wristband to be used by itself, and is interchangeable with other styles of Buddy Tag wristbands.