Fitbit Charge 3Garmin Vivosport
Tech specs 
SizeDevice Dimensions: 35.8mm x 22.7mm x 11.8
One size (small and large bands included)
Width: 21.0 mm
Thickness: 10.9 mm
MaterialBuilt of more lightweight material including an aerospace grade aluminum case and Corning Gorilla Glass 3 display. The housing and buckle are made of anodized aluminum.Case material: fiber-reinforced polymer
Lens material: chemically strengthened glass
ChargingUSBUSB
BatteryLithium-polymerRechargeable lithium-ion
Battery lifeup to 7 daysGPS mode: Up to 8 hours
Smartwatch mode: Up to 7 days
Water-resistance5 ATMSwim
Weight29 gramsSmall/medium: 24.1 g
Large: 27.0 g
SensorOptical heart rate tracker, 3-axis accelerometer, altimeter, SpO2, vibration motorGPS, barometric altimeter, compass, accelerometer, heart rate
DisplayOLED full touchscreen, TFTsunlight-visible, transflective memory-in-pixel (MIP), 72 x 144 pixels
Screen size35.8mm x 22.7mm9.7 mm x 19.3 mm
ColorsMultipleSlate, Limelight, Fuchsia Focus
OtherNFC (Special edition)
Connectivity: Bluetooth, WiFi
Charge 3 stores your stats and data for 7 days in between the times you sync your tracker.
MEMORY: 7 timed activities, 14 days of activity tracking data
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYesYes
SleepYesYes
Heart rate24/7 + HRV (premium subscription)Yes
Stress & recoveryYes
Pulse OxYes
Respiration rateYes (premium subscription)
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPSYes
Running featuresPreloaded running profiles, GPS based distance/time/pace
Swimming features
Other Guided breathing, Female Health Tracking- all day stress tracking
- gym workout tracking
- music control, find my phone, etc.
- Built in apps for running, cycling, cardio, walking, strength training, rep counting, stair-stepper.
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storage
Connected payYes (special edition)
LTE
Links 
Affiliate link*AmazonAmazon
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