The Medela Swing Single Electric Breast Pump is for women searching for a lightweight, reliable, occasional use solution for singe pumping. Designed to deliver easy and convenient breast pumping at home, at work, or anywhere you travel. This simple to use breast pump receives power from an included AC power adapter or can be powered by batteries for the perfect on-the-go option. This single motor breast pump is infused with patented and research-based 2-Phase Expression Technology. Through research, Medela has learned that there are two distinct phases of how babies breastfeed. The stimulation phase is when babies first go to the breast, where they suck faster to start milk flowing.