Fitbit Inspire 3. Device type: Armband activity tracker, Form factor: Rectangle, Product colour: Black. Heart rate sensor type: Optical, Memory capacity: 7 day(s), Daily totals memory capacity: 30 day(s). Charging time: 2 h. Width: 18.6 mm, Depth: 39.3 mm, Thickness: 1.18 cm. Mobile operating systems supported: Android, iOS