Will your dog work for food? This egg-shaped activity ball mentally and physically stimulates dogs by appealing randomly dispensing kibble and treats as the ball tumbles around. The Kibble Nibbler also features rubber bumpers to minimize noise and marks on walls and floors. Unscrews for easy loading and quick cleanup. Dishwasher safe. Small is sized for dogs under 20 pounds and holds 1 cup of food. Medium/Large is sized for dogs over 20 pounds and holds up to 2 cups of food.