Q&AQuestion:With the other nipples, you have to poke a hole for the air vent. Do you have to do that to these as well?Answer:There is a vent specifically molded into the silicon at the base of the nipple to allow for great milk . Poking additional holes may cause unwanted leakingQuestion:How long can this product be used?Answer:Indefinitely, as long as it's kept in good condition.Features: 1. Designed for calf, the rubber nipple is similar to cow's milk, making it easy for calf to eat. 2. With handle design, easy to feed. A great tool of weaning small animals from their mothers gradually. 3. 4L capacity, sufficient for daily consumption of calves. 4. The bottle body is made of premium plastic, thickened, , healthy, for long term use. 5. Comes with regulating valve to control milk rate. Specification: Condition: Brand New Item Type: Calf Nursing Bottle Main Material: Plastic Product Color: White Product Capacity: 4L Suitable for Animal Type: Calf Package List: 1 * Calf Nursing Bottle Note: Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.