Medela Pump In Style Advanced Backpack has 2-Phase Expression Technology research-proven for faster milk flow in less time, allows moms to change back & forth from stimulation to expression. Updated bag design with contrast color accent. PersonalFit breastshields. New bottle design. Integrated motor. -Daily use. Includes AC Adapter and Battery Pack (8-AA sold separately), or use with 9 Volt Vehicle Lighter Adapter (sold separately).