• Always-on wellness tracking
• Stress Management Score
• Daily Readiness Score Premium only
• Sleep Profile Premium only
• Up to 10 day battery
• Active Zone Minutes
• High/low heart rate notifications
• Irregular heart rhythm notifications  
• Blood oxygen (SpO2)
• More insights with Fitbit Premium

Specifications:

• Dimensions (L × W × H/D): 14.96 cm × 1.86 cm × 1.17cm (5.89 in. × 0.07 in. × 0.04 in.)
• Weight: 0.017kg (0.039 lb.)

Warranty: 1 year