My baby loves the wide base nipple, but as the previous customer stated you do need a wide base collar. They don't sell them in the stores yet, but you can call the Medela and they'll mail you some for free. Great customer service! The part number for the Wide Base collar is 2001485, and the phone number for Medela Customer service is: 800-435-8316.Get more detail about Medela Wide Base Nipples 3-Pack Medium Flow #87134.
