The KONG SqueakAir Ball puts a squeaker inside a tennis ball, so one toy covers fetch and chew. The felt is KONG's own non-abrasive tennis material, which matters more than it sounds: real tennis-ball fuzz is abrasive and grinds down a dog's teeth over time, and this does not. The squeak keeps a dog interested between throws. Two Large balls per pack, about 3.25 inches across, for big dogs that make short work of a regular ball.