Swim-proof to wear in the shower ocean or pool. Tracks steps distance calories burned and more. Fitbit app – use to see workout summaries set goals and more. Tracks sleep quality and length. SmartTrack auto recognizes select exercises. Reminders to move. Receive smartphone notifications. LED Display. Removable tracker. Syncs wirelessly via Bluetooth to any iOS Android or Windows devices. Built-in rechargeable lithium-polymer battery. Includes 2 wristbands and a charging cable. Small band fits 5.5″ – 6.7″. Large band fits 6.7″ – 8.1″.