Fitbit Charge 2Garmin Vivosmart 3
Tech specs 
SizeWidth: 21mm
Small: 14 cm - 17 cm in circumference
Large: 16.5 cm - 20.6 cm in circumference
XL: 20.6 cm - 23.6 cm in circumference
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 mm
MaterialFitbit Charge 2's wristband is made of a flexible, durable elastomer material similar to that used in many sports watches. Fitbit Charge 2 also has a surgical-grade stainless steel buckle.Silicone
ChargingUSB. Charge time: One to two hours.USB
BatteryLithium-polymerLithium battery
Battery lifeup to 5 daysUp to 5 days
Water-resistanceSweat, rain and splash proof.Up to 50 metres (5 ATM)
Weight36 gramsSmall/medium: 20.4 g; Large: 21.5 g
SensorOptical heart rate tracker, 3-axis accelerometer, altimeter, vibration motor3 axis-accelerometer, barometric altimeter, heart rate monitor, vibration alert, ambient light sensor
DisplayOLEDOLED
Screen size3.8 cm9.6 mm x 19.2 mm, 64 x 128 pixels
ColorsBlack, Plum, Blue, Teal, Lavender Rose Gold, Black/Gunmetal Black, Purple
Other
Activity tracking 
StepsYesYes
DistanceYesYes
CaloriesYesYes
ActivityYesYes
FloorsYesYes
SleepYesYes
Heart rate24/724/7
Vo2MaxYesYes
Stress & recoveryYes
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPS
Running featuresAccelerometer (calculates distance for indoor workouts, without need for a foot pod), personal records.
Swimming features
Other Guided breathing- stress monitoring
- automatic rep count in the gym
- Clock, music control, auto goal, move bar
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storage
Connected pay
Links 
Affiliate link*Amazon | FitbitAmazon | Garmin
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