We already had wide Nuk nipples from our last child. They also work on the born free bottles as long as you use the born free vent system as well. Nice not to have to switch nipples and pacifiers as the new baby had gotten used the Nuk orthodontic shape. I tried to hunt down this information when I bought the born free bottles a couple of months ago, but couldn't find any news that they would work. I was desperate and took the chance. Thankfully they work!