The Garmin vivosmart 4 is a slim, screen-light fitness and sleep tracking band rather than a full smartwatch — this is the Large-size Black/Slate worldwide edition, fitting wrists from about 148-215mm. It uses a small 6.6 x 17.7mm OLED touchscreen display at 128 x 48 pixel resolution set into a silicone band with an aluminium bezel and metal accents, weighs about 17g, and is rated to 5 ATM water resistance for swimming and showering. Its standout feature at launch was a red-LED Pulse Ox sensor for overnight blood oxygen saturation tracking alongside on-demand daytime readings, plus three-stage sleep tracking (light, deep, REM) and sleep movement tracking. Other health tracking includes the Elevate wrist heart rate sensor, stress tracking, Body Battery energy monitoring, and a built-in barometric altimeter. It relies on Connected GPS via a paired phone for outdoor activity distance/pace (there's no onboard GPS chip), broadcasts heart rate over ANT+, and does not support NFC or Garmin Pay. Battery life runs up to 7 days on a charge. This suits buyers who want lightweight, minimal-footprint sleep and activity tracking rather than a full-featured GPS sports watch.