Merrick's Super-Calf Nipples feature the first advance in calf nursing nipple design in many years. Incorporated into the nipple design is a patented air release valve, which prevents leakage and yet allows air to be released into the bottle as the calf is nursing. This ensures the proper flow of milk through the nipple to the nursing calf. This valve is protected with extra "bumpers" for even longer wear. In addition, the surface of the Super-Calf Nipple has been specially treated to promote ease of use.