Worked great for me! No flaws, holds battery charge perfectly. Comes with the 24 mm size flanges. Charger included along with backpack. The Spectra® S1 Plus™ Premier Rechargeable double electric breast pump provides all the features of the S2 Plus™, but with a built-in 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. Like all Spectra® pumps, the S1 Plus is a closed system – a physical barrier between the milk and the pump ensures hygiene and motor performance. With a maximum suction strength of 270mmHg and the ability to be used as a single or double pump, the S1 Plus is the ultimate breastfeeding solution with everything you need to get started. The S1’s completely flexible, one-touch button and digital controls allow you to set the pumping program to the speed and rhythm most effective for your body. The suction is adjustable in both let-down and expression modes. This quiet pump also includes a timer and night light. Features & Benefits: Single or Double Pump capability Vacuum suction up to L12 270 mmHg Weighs only 3 lbs. Built-in night light LCD screen