Learn to manage stress, sleep better and live healthier with Sense 2—our most advanced health and fitness smartwatch.Operating temperature : 14° to 113° F (-10° to 45° C)..Band material type : Silicone Manage stress and live healthier: all-day stress detection with cEDA and daily Stress Management Score, ECG app for atrial fibrillation assessment(1), irregular heart rhythm notifications(2), SpO2(3), health metrics dashboard(4), mindfulness content Measure and improve sleep quality: personalized Sleep Profile(5), daily sleep stages & Sleep Score, smart wake alarm and do not disturb mode Enhance activity: built-in GPS and workout intensity map, Daily Readiness Score(5), Active Zone Minutes, all-day activity tracking and 24/7 heart rate, 40+ exercise modes and automatic exercise tracking, water resistant to 50 meters Designed for all-day wear: on-wrist Bluetooth calls, texts and phone notifications(6), customizable clock faces, Fitbit Pay(7), Amazon Alexa built-in(8), Google Wallet & Maps (Google Maps on Android only, coming Spring 2023 to iOS), 6+ day battery(9) Sense 2 is sleek and slim with raised band attachments that make it more comfortable for all-day wear. Both small and large sizes included in box. Small: Fits wrist 5.1 - 7 inches in circumference. Large: Fits wrist 6.5 - 8.6 inches in circumference Includes a 6-month Premium membership complete with personalized insights, advanced analytics and more (New & returning Premium users only. Must activate trial within 60-days of device activation. Content and features may change)