Fitbit Inspire HRGarmin Vivosmart 4
Tech specs 
SizeDevice Dimensions: 16.2 mm x 12.6 mm x 37 mm (W x D x L)
Small band: Fits wrists 140 mm - 180 mm in circumference
Large band: Fits wrists 180 mm - 220 mm in circumference
Width: 15mm
Depth: 10.5mm
Small/medium: 15 x 10.5 x 197 mm (fits wrists with a circumference of 122-188 mm)
Large: 15 x 10.5 x 223 mm (fits wrists with a circumference of 148-215 mm)
MaterialThe housing is plastic. The classic band is made of a premium, comfortable silicone similar to that used in many sport watches, and the buckle is made of anodized aluminum.Polycarbonate lens, aluminium bezel, silicone strap
BatteryLithium-polymerLithium battery
Battery lifeup to 5 days. Charge time (0-100%): Two hours.Up to 7 days
Water-resistanceup to 50 metres (swim-proof) - 5 ATMUp to 50 metres (5 ATM)
Weight20 gramsSmall/medium: 16.5 g
Large: 17.1 g
Sensor3-axis accelerometer, vibration motor, optical heart rate sensor3 axis-accelerometer, barometric altimeter, heart rate monitor, vibration alert, ambient light sensor, Pulse Ox
DisplayGreyscale OLED TouchscreenOLED
Screen size37 x 16mm0.26" x 0.70" (6.6 mm x 17.7 mm), 48x128 pixels
ColorsBlack, Lilac, White/BlackVarious
Other- Saves 7 days of detailed motion data – minute by minute
- Saves daily totals for the last 30 days
Activity tracking 
Calories burnedYesYes
SleepYes (light, deep, REM)Yes
Heart rateYes (Stores heart rate data at 1 second intervals during exercise tracking and at 5 second intervals all other times)24/7
Stress & recoveryYes
Pulse OxYes
Respiration rate
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPSConnected GPS
Running featuresAccelerometer (calculates distance for indoor workouts, without need for a foot pod), personal records.
Swimming features
Other Vo2Max/Cardio Fitness Level, 15 goal-based exercise modes, as well as breathing exercises.- Body Battery™ Energy Monitor
- automatic rep count in the gym
- Clock, music control, auto goal, move bar
Non-fitness functions 
Smartphone notificationsCall, text and calendar notificationsYes
On-board music storage
Connected pay
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