Designed for the tech-savvy and style-conscious pet owner, the Nina Woof Cupertino Dog Collar combines modern design with functionality. This collar is fully compatible with Apple AirTag 2021, so your pet s location is always just a tap away (AirTag not included). Available in four convenient sizes to fit dogs of all breeds:Extra Small: Neck 9"–12", Width 0.7", Length 16.4"Small: Neck 12"–15", Width 0.7", Length 19"Medium: Neck 15"–19", Width 1", Length 21.7"Large: Neck 19"–23", Width 1", Length 25"For best results, measure your pet s neck and check our sizing chart before purchasing to ensure the perfect fit.