Fitbit Sense 2 Health & Fitness Watch – Lunar White | FB521SRWTAll-day body-response tracking with a newly added sensorSleep Profile and breakdown of time in light, deep & REM sleep to see what’s impacting your rest (Premium only)ECG appBlood oxygen (SpO2)Notifications for call, text and apps (Available when phone is nearby)6+ day battery life (Varies with use and other factors)