The Evenflo Feeding Advanced Single Electric Breast Pump is compact, portable, and designed for occasional-use pumping. This travel-friendly pump can be powered via the included AC Adapter or AA Batteries (sold separately). To help keep you comfortable, multiple flange sizes (28.0mm & 30.5mm) are included with your pump. The flange is the part of the pump you place against your breast. A proper flange fit is important - it not only gives you a comfortable, more gentle pumping experience, but also equates to more milk. If the flange does not fit properly, you may experience discomfort and/or a decrease in your milk expression. The closed system design makes this pump hygienic, easy to clean, and helps prevent milk back up in the pump motor, keeping parts clean, dry, and functioning properly. With control at your fingertips, you can easily adjust the pump's suction and turn the pump on and off using one dial. If you need assistance, our team of Breastfeeding Experts are available for one-on-one product and pumping support. In addition, we encourage you to register your breast pump to access your breastfeeding and breast pump education.