The Chuckit! Fetch Medley 2 is a refreshed assortment of the best-selling Chuckit! Fetch Medley and includes a Chuckit! TPR Strato Ball, an Erratic Ball with squared corners to keep the bounce trajectory changing and an Ultra Squeaker Ball, our classic rubber ball with a squeak! Medium size balls are compatible with your dog's medium Chuckit! launcher.