Garmin 010-N1995-00 Refurbished vivosmart 4 Activity Tracker, Small/Medium, Black/SlateStylish, smart design This slim wristband tracker, available in multiple colors, complements your style with its distinctive design, metal trim accents and bright, easy to read display Pulse Ox at your wrist the Pulse Ox sensor on vvosmart 4 estimates your bodys blood oxygen saturation level. Advanced sleep monitoring to give you an idea of how youre sleeping, vvosmart 4 tracks your light, deep and REM stages of sleep, along with movement throughout