Great nipple for a pop bottle to feed kids or lambs. Incorporates a ball valve to allow inlet of air, but the ball will not fall out and get lost! The pop bottle nipple will fit all standard plastic pop and soda bottles. The Excal nipple is long-lasting. Will rear quite a few lambs or kids without breaking. Lambs and kids love it. The design makes it easier to transition to the Milk Bar or Caprine feeders. To speed up the flow for stronger lambs, just open the tip x-cuts slightly. Recycle any plastic soft drink bottle by adding this cap and nipple and create a lamb nursing bottle. Satisfaction guaranteed! LFET