Tracks steps distance calories burned and active minutes. SmartTrack records activity in Fitbit app. Monitors sleep and provides silent alarm. Reminders to move. Smart notifications. Battery lasts up to 5 days. Water sweat rain and splash proof. Syncs stats wirelessly and automatically. Tracks 5 detailed days and totals for 30 days. OLED Tap display. Large: Fits wrists 6.7″-8.7″ in circumference. 1-Year manufacturer limited warranty. Compatibility: iPhone 4S and later. iPad 3 Generation and later. Leading Android and Windows devices.