Nurtria wide neck bottle silicone nipples are made of ultra soft silicone to be gentle on your infant's mouth and gums. All Nurtria nipples will fit any Nurtria bottle, but will also fit most other wide neck bottles as well. Available in 3 different flow rates: Fast flow for 6 months and up, medium flow for 3 months and up, and slow flow for newborn and up, the Nurtria silicone nipples are also available in a vari flow design as well to allow your child to control the rate of flow while feeding.