Fitbit IonicFitbit Versa 2
Tech specs 
SizeWatch Width: 38mm
Watch Thickness: 12mm
Screen size 40 x 40mm
Small: Fits wrist 140 mm - 180 mm in circumference
Large: Fits wrist 180 mm - 220 mm in circumference
Material- Strong & lightweight 6000 series aerospace-grade aluminum.
- The wristband is made of a flexible, durable elastomer material
The classic band is made of a flexible, durable material similar to that used in many sports watches, and includes an aluminium watch case and buckle. The woven band is made from a comfortable polyester and includes an aluminium watch case and buckle.
ChargingUSBUSB
BatteryLithium-polymerLithium-polymer
Battery life4+ days with a GPS battery life up to 10 hours (1-2 hours charge time)5+ days. Charge time (0-100%): 2 hours.
Water-resistanceup to 50 metres (swim-proof) - 5 ATMup to 50 metres (swim-proof) - 5 ATM
Weight50 grams40 grams
SensorAltimeter, 3-axis accelerometers, digital compass, GPS, optical heart rate monitor, ambient light sensor, pulse Ox, vibration motor.3-axis accelerometer, Optical heart rate monitor, Altimeter, Ambient light sensor, Vibration motor, Wi-Fi antenna (802.11 b/g/n), Relative SpO2 sensor, temperature sensor, NFC, Built-in microphone
DisplayHi-res touchscreen (up to 1000 nits). Corning Gorilla Glass 3 display.Colour AMOLED touchscreen, 300 x 300 pixel resolution
Screen size29 x 21mm, 348 by 250 pixels1.4 inches
ColorsComes is Sport, Leather and Classic versions.Comes in a number of colours. Also there's a regular and special edition (which comes with an additional woven band and 90 day trial to Fitbit Premium).
Other- Saves 7 days of detailed motion data – minute by minute.
- Saves daily totals for past 30 days
- Saves 7 days of detailed motion data, minute by minute
- Saves daily totals for the last 30 days
- Stores heart rate data at 1-second intervals during exercise tracking and at 5-second intervals all other times
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYesYes
SleepYes (light, deep & REM)Yes (light, deep & REM)
Heart rateYes + HRV (premium subscription)Yes + HRV (premium subscription)
Stress & recovery
Pulse OxYesYes
Respiration rateYes (premium subscription)Yes (premium subscription)
UV exposure
Skin temperatureYes (premium subscription)Yes (premium subscription)
Galvanic skin response
Hydration level
Calorie intake
GPSGPS/GLONASS
Running featuresPace, distance & routes
Swimming featuresLap count, duration & calorie burn
Other - Guided breathing sessions
- Female health tracking
- Guided breathing sessions
- Female health tracking
Non-fitness functions 
Smartphone notificationsCall, text and calendar notificationsCall, text and calendar notifications
On-board music storageYes, 2.5GB (300 songs) + access PandoraYes, 2.5GB (300 songs) + access Pandora, Spotify, Deezer
Connected payYesYes
LTE
Links 
Affiliate link*AmazonAmazon
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