The JW? Pet Sand Perch Swing is specially designed for your pet birds well-being and comfort. Your feathered friend will get a great workout as he exercises the muscles in his feet. It is thicker at the ends and slender in the middle to give your birds feet a workout with different grip sizes. A natural sand feel and rough texture provide an excellent surface for normal wear of your pet birds nails. The swing easily attaches to cage ceiling wire. Small is sized right for parakeets and similar sized birds. Regular is sized right for cockatiels and similar sized birds.