Spectra S1 Plus Black Tote Breast Pump Kit providing all the features of the S2, with the addition of an inbuilt rechargeable battery. This means that you are now able to benefit from the efficiency, power and performance of a hospital strength breast pump, without compromising on portability. It has closed system which has a physical barrier between the milk and the pump ensures hygiene and motor performance. It has maximum suction strength of 250mmHg and the ability to be used as a single or double pump. The backflow protection helps to protect breast milk and baby from bacteria, mold and viruses while pumping, keeps tubing dry by preventing air flow between expressed milk and pump tubing while pumping, no need to clean the narrow tubing.