We're using the Playtex system, but wanted to let you know that my 10.5 WO DD can take 45 minutes to eat 3.75 ounces. She likes a breather between the appetizer (first ounce), the main course (second and third ounce), and dessert (last bit). But, she'll loll the nipple around in her mouth and let it drip out. Or she'll get passive agressive with it and attack the nipple, then arch her back, thrust her legs and cry out. But, if I take the bottle away she cries for it back. Very strange kiddo! If you can, let me know how it goes. Maybe I should adjust the nipple too.