Regular exercise keeps dogs happy and healthy. The K9 Fitness by Zeus ball tug toy will keep your dog engaged and entertained with a variety of stimulating textures. Flexible TPR ball is soft on teeth and gums. Inner tennis ball will drive dogs wild and entice play. Additionally, dogs see shades of blue and yellow. The K9 Fitness by Zeus collection was particularly designed with that in mind. The toys' blue and yellow colors can easily be located by your dog regardless of the environment they are playing in.