Whistles When Launched: This 2.5" dog ball is designed with four sound holes that create a whistling sound, making fetch more exciting for dogs. Recommend using any size Medium Chuckit! launcher; casually tossing The Whistler will not yield loud whistles Super High Bounce: This Chuckit! ball for dogs is made of durable rubber yielding an ultra bouncy, exciting fetch experience. Not designed to float, land use only; not a chew toy, always supervise your dog when playing with this toy Sizing matters: Size medium measures 2.5" in diameter and is best suited for dogs weighing 20-60lbs. Dog balls should be small enough for your dog to carry, but large enough that the ball can't completely fit in their mouth. When in doubt, buy a size up Make Fetch Happen: Chuckit! Performance toys are designed with you and your dog in mind; Try our full range of indoor and outdoor interactive dog toys including tumblers, flyers, fetch toys, other balls for dogs and more Chuckit! Fetch Pet Toys: Chuckit! makes indoor and outdoor dog toys that enrich the human-animal bond and helps dogs and puppies stay engaged. Try our full line of ball launchers, puppy toys, flying discs, tennis balls for dogs, dog chew toys, and more