Spots-Light harnesses are designed for medium and small dogs. The Medium Harnesses are fully adjustable and will fit dogs the size of a Jack Russel, Spaniel, Terrier and Poodles. The small harnesses has been designed for the small to tiny dogs. They both light up all the way around and allow even the small dogs to be seen. Most small dog owners prefer a Harness vs a Collar so we offer the best product on the market to keep your puppy safe.