These nipples are designed to fit snugly on a standard 20-ounce plastic soda bottle. The nipple is soft and pliable, with a natural shape for the tender mouths of lambs, kids, piglets, foals, and other small livestock. Made with a special rubber formula to prolong nipple life and improve pliability. Each nipple is 0.55 inch diameter by 2.5 inch long, with a 1.38 inch thumb tab.