The Medela Harmony Flex is a manual breast pump designed for occasional use and travel. It features a PersonalFit Flex breast shield that adapts to your breast shape for comfortable and efficient pumping. Being manual, it's quiet and discreet, providing moms with control over suction and pace. 'Ready Stock' indicates immediate availability, and 'many sizes available' suggests the pump comes with a variety of shield sizes to ensure optimal fit and comfort.