Which Philips Avent original Natural nipple suits my baby best?

Nipples are available for 0m, 0m+, 1m+, 3m+ and 6m+. See the image below for an overview. These Philips Avent Natural nipples can be used on the Natural Philips Avent feeding bottle and Philips Avent storage cup. 

• The Natural First Flow nipple (with the number 0 on the nipple) is recommended for newborns and preemies. This nipple can be used from day 1 and when switching from breastfeeding to bottle-feeding. 
• The Newborn nipple (with the number 1 on the nipple) is recommended for babies of 0+ months old who are breastfed and bottle-fed.
• The Slow Flow nipple (with the number 2 on the nipple) is recommended for babies of 1+ months old that are breastfed and bottle-fed.
• The Medium Flow nipple (with the number 3 on the nipple) is recommended for babies of 3+ months old.
• The Fast Flow nipple (with the number 4 on the nipple) is recommended for babies of 6+ months old.
• The Variable Flow nipple (with the I, II, and III markings on the nipple) is suitable for babies aged 3+ months old. This nipple has a slot cut into it which provides an adjustable flow rate. The flow rate can be varied by turning the bottle to align the I, II, or III markings on the nipple with the baby's nose.

Once the consistency becomes too thick for these nipples, we recommend you to use the Philips Avent Thick Feed nipple.

• If you are breastfeeding, we suggest staying with the Natural First Flow nipple because it is designed to match the flow rate of the mother.
• If your child becomes frustrated at meal times, you may see them suckling hard, then pulling away, crying, and suckling hard again. When your baby is taking longer than 20 to 30 minutes to finish a bottle, this may be an indication that the flow is too slow. If this is the case, change to a nipple with a higher flow rate.
• If your baby lets go of the nipple, is spilling milk, is getting too much milk to swallow, or milk is dripping between the lips and the nipple, the flow rate might be too fast. Change to a nipple with a lower flow rate.

You can also use the Natural nipples with a screw ring in combination with the Classic/Classic+ feeding bottles.