Step Up Is The Only Feeding Bottle That Allows You To Feed Your Baby Naturally Throughout Every Growth Phase As It Is The Only Bottle That Is Able To Adapt To The Changes In The Sucking Action Of The Baby Over Raised Rings: To Help The Baby Find And Maintain The Correct Position Of His Tongue And Simulates The Wrinkles Of A Mother?S Nipple. An Extra-Large And Soft Base To Ensure Maximum Simulation Of The Maternal Breast Available Flows: Step Up 2 2M+ 250 Ml : Adjustable Flow?Step Up 2 4M+ 250 Ml: Fast Flow The Non-Angled Shape Of The Teat Is Ideal From 2 Months Onwards, When The Colic Episodes Have Subsided? Raised Rings: They Help The Baby Find And Maintain The Correct Position Of His Tongue And Simulates The Wrinkles Of A Mother?S Nipple.? An Extra-Large And Soft Base To Ensure Maximum Simulation Of The Maternal Breast? Short Teat Specifically Designed For Newborns. ?With Anti-Colic Valve