The Rhythm™ Dual Action Electric Breast Pump closely mimics breastfeeding while maintaining efficiency and comfort. It features a fast rhythm to encourage milk flow, and a slow rhythm that gently expresses the milk after flow has begun. Some women require more use of the fast rhythm, and some require more use of the slow rhythm. Whatever your rhythm is, we have a setting for you. That's because you can set the programming unit to remember your unique combination of fast and slow. That way, the next time you need to express, all you need to do is sit back and relax. You can also choose to run your breast pump off the battery pack*, or a standard wall outlet which make it perfect for home or travel.