Purchased for $250. Used for less than a year. Each sock is washed and clean. Comes with FOUR socks. Two < 12lbs (right and left foot), two 12-30lbs socks (one right foot and one left foot). This is the third gen Owlet sock that show both heart and oxygen rate. The oxygen was my absolute favorite with our twins, especially when they got sick. It allowed us to see just how low their oxygen saturation got and when to take them into the pediatrician. Android users can use the Owlet Care app with this sock. Apple users will need to download the Owlet Web App. The Owlet sock and base station will still work as normal and alert you if levels dip. You can also actively check baby’s heart rate and oxygen levels from the Owlet Web App when you open it. You will still hear a lullaby from the base station if baby's sock is loose and a very loud alarm if heart rate or oxygen drop too low.