Compatible with the Orangetheory Fitness app for use during in-studio, at-home and out-of-studio workouts. The OTbeat Burn measures distance, calories, and your unique heart rate data so you can get the most of your workout. It has a sleek, black band that can be worn on your wrist, forearm, or bicep. The box includes OTbeat Burn heart rate monitor ONE black armbands in size Large only. Can purchase smaller band for about $7-10. Mini-USB Charging Cable