Sleek, form-fitting activity tracker with a hidden display and Garmin Elevate wrist heart rate technologyTracks steps, distance, floors climbed, intensity minutes and sleep. Counts reps, sets and rest time. Activity profiles for walk, run, cardio and moreFitness Age and VO2 Max, a measurable indication of your aerobic performance or fitness level,Physical size-Width: 18.5 mm,Thickness: 9.8 mm,Length (small/medium): 197 mm,Length (large): 223 mm,Circumference (small/medium): 122-188 mm,Circumference (large): 148-215 mmAll-day stress tracking, which lets you keep tabs on your stress level throughout the day. Safe for swimming and showeringSmart notifications include alerts for calls, texts, social media, music, games and weather. 5ATM (50 m) water resistant and 5-plus day battery life,With connectivity to a phone, its often found a simple reset of the phones Bluetooth or turning the phone on and off will resolve any Bluetooth issues that arise.