Milk Bar Bottle Nipple fits most standard calf nursing bottles with top OD from 2.25 to 2.6 inches (57 to 67mm). Designed to replicate a cow"s teat, the Milk Bar^tm Nipple provides milk at the proper rate to stimulate saliva production which is essential for nutrition and for the development of the calf"s digestive system. Other nipples cause calves to gulp, providing too much milk too quickly and discouraging salivation, but the Milk Bar^tm Nipple gives a perfect flow of milk. Milk Bar^tm Nipple fits any of our snap-on style nursing bottles.