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Shadow grey aluminium smartwatch with silicone band, square AMOLED display

Fitbit

Fitbit Sense 2 FB521BKGB-US Shadow Grey Graphite Aluminium smart watch

SKU CH-65RS-9WEQB MPN FB521BKGB-US

Tracks health, stress and sleep with ECG, SpO2 and cEDA sensors, offers six-plus day battery and includes both band sizes

  • Battery runtimeof 6+ days. Battery life and charge cycles vary with use, se
  • Housing materialAluminium
  • Strap materialSilicone
  • Strap lengthBoth small and large sizes included in box. Small: Fits wris
  • Display typeAMOLED
  • Internal storageSaves 7 days of detailed motion data, minute by minute

Color Shadow Grey

  • 6+ days battery life with 12-minute quick charge
  • cEDA sensor tracks body response for stress management
  • ECG app checks heart rhythm from your wrist
  • Built-in Amazon Alexa handles alarms and weather hands-free
  • Contactless payments let you pay directly from the watch

Fitbit Sense 2 Shadow Grey smartwatch

The Fitbit Sense 2 is a health-focused smartwatch with a Shadow Grey aluminium case and AMOLED display. It tracks heart rate, skin conductance and ECG data for adults who want continuous wellness monitoring. Both small and large silicone bands are included to fit wrists from 5.1 to 8.6 inches. The watch stores seven days of detailed motion data on the device.

Compatibility and account requirements

A Google account is required to activate the watch and the Fitbit app must be installed on a compatible smartphone. The ECG app and irregular rhythm notifications are only available in select countries and are not intended for people under 22 years old. SpO2 tracking and Health Metrics dashboard access also vary by region and may require a Fitbit Premium membership.

Battery life and charging

Battery life reaches 6+ days under typical use, though always-on display, SpO2 and the cEDA sensor reduce that figure. A full day of charge can be added in 12 minutes using the supplied cable. The case measures 0.44 in thick and weighs 0.08 lb, so it remains light during continuous wear.

How it compares

Measured against everything we stock in Smartwatches & Fitness Watches, at today’s prices. Recalculated every night.

Price $185.99
Pricier than about 75% of the 346 comparable items (median $82.49).

Specifications

Product
Brand nameFitbit
Model nameSense 2
Part numberFB521SRWT-US
Product colorShadow Grey
Product typeSmart Watch
Storage
Internal storageSaves 7 days of detailed motion data, minute by minute
Display
Display typeAMOLED
Size & build
Housing materialAluminium
Strap materialSilicone
Strap lengthBoth small and large sizes included in box.
Small: Fits wrist 5.1–7 in in circumference
Large: Fits wrist 6.5–8.6 in in circumference
Overall height0.44 in (11.2 mm)
Overall width1.59 in (40.5 mm)
Product depthLength: 1.59 in (40.5 mm)
Product weight0.08 lb (37.64 g)
Shipping weight0.19 kg
Package size51 × 51 × 25 mm
In the box
Included itemsFitbit Sense 2
Classic band (small & large)
Charging cable

Other versions of this model

1 more in the same range

Questions about this item

What bands and accessories come in the box and is anything else needed to start using it?

The box contains the Sense 2 watch, a classic silicone band in both small (5.1‑7 in) and large (6.5‑8.6 in) sizes, and a charging cable. A Google account and the Fitbit app on a compatible phone are required for setup.

Which band size should I choose for my wrist circumference?

The small band fits wrists from 5.1 to 7 inches around; the large band fits 6.5 to 8.6 inches. Both sizes are included, so you can swap to the one that feels secure and comfortable.

What does the 6+ day battery claim mean when I use always‑on display, SpO2 and the cEDA sensor?

The 6+ day figure is a baseline; enabling always‑on display, SpO2 tracking or the cEDA body‑response sensor will reduce runtime and require more frequent charging. A 12‑minute charge adds a full day of use.

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