LCD display provides status of programs and functions.. Control suction and speed to suit your comfort level with a total of 28 pumping state options.. Two-phase expression; stimulation and expression mode.. Easy to assemble and clean; silent for discreet pumping. Passive prevention of milk backflow. Single or double pumping options. Piston Pump System imitates baby's sucking rhythm.. Includes A/C power supply and external battery pack six AA alkaline batteries (not included). One-year limited warranty.