Fitbit Alta HRFitbit Charge 2
Tech specs 
SizeDevice Dimensions: 15 mm x 10 mm x 35 mm (W x D x L)
(Sizes depend on type of band)
Width: 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
MaterialWristband is made of a flexible, durable elastomer. The tracker is made with surgical-grade stainless steel, and the buckle is made with aluminum.Stainless steel casing, elastomer strap
Battery lifeup to 7 daysup to 5 days
Water-resistanceSweat, rain and splash proofSweat, rain and splash proof.
Weight15 grams36 grams
Sensor3-axis accelerometer, Vibration motor, optical heart rate sensorOptical heart rate tracker, 3-axis accelerometer, altimeter, vibration motor
DisplayB&W OLED touchscreenOLED
Screen size1.4-inch, 128 x 36 pixel resolution3.8 cm
ColorsBlack, Blue/Gray, Coral, FuchsiaBlack, Plum, Blue, Teal, Lavender Rose Gold, Black/Gunmetal
Activity tracking 
Calories burnedYesYes
Heart rate24/724/7
Stress & recovery
Pulse Ox
Respiration rate
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPS
Running features
Swimming features
Other Clock, auto sleep detection, silent wake alarm, auto exercise recognition.Guided breathing
Non-fitness functions 
Smartphone notificationsYesYes
On-board music storage
Connected pay
Affiliate link*Amazon | FitbitAmazon | Fitbit
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