Comes with clear, snap-on nipple with insert. Made of high-quality synthetic rubber to clearly see inside the nipple. Helps eliminate wasted milk while nursing. Embedded silicone membrane will only let milk pass while calf is suckling, functioning naturally like a real cow’s teat. Insert features a round opening at the tip of the nipple. 2 mm hole controls milk flow while calf is latched, increases longevity and eliminates tearing. Narrow neck and soft-touch synthetic rubber closely mimic a cow’s teat, promoting nursing for adequate feeding.