Z2 Double Electric Breast PumpThe Z2 rhythmically alternates expression between breasts to increase stimulation and express more milk in less time. The modes mimic the way baby feeds, with extra stimulation that helps increase milk products. The mode starts out with an initial flutter suction pattern, followed by a stronger extraction without having to switch settings. It offers three different pumping styles that you can tailor for comfort: Massage, Expression, and 2 Phase mode