Parents cannot always rock babies as rocking chairs do, nor swing them like swings. We believe that infant seats would be a better choice if they could mimic the natural movements that parents make to soothe their babies, and that's why 4moms invented the Mamaroo infant seat. We had parents wear clothes with sensors to understand those movements, then we simulated the rocking and swinging movements in the Mamaroo chair to soothe and entertain your baby better than traditional infant seats. It vibrates up and down and swings side to side like parents do. 5 speeds and 5 unique movements: vibrates up and down, and swings side to side like parents do to soothe their babies Built-in sounds, and MP3 player connection: choose from 4 soothing sounds for the baby or play your favorite songs Bluetooth connectivity: to control movement and sound through your compatible smart device. No battery needed, just plugs into the wall Adjustable seat recline to full recline Reversible play balls. Machine washable fabric The balls are just missing, but the device is working perfectly.