Optical heart rate sensors work by using light to measure blood flow in capillaries beneath the skin. The top of your wrist is a convenient place for a watch, but is a challenging location for even the best sensors. Wearing on the arm offers our optical sensor an optimal amount of blood flow to gather heart rate data with accuracy equivalent to that of a traditional chest strap.Simpler to wear than a chest strap, the soft fabric band lays flat around your arm and locks in place with its textured surface. The low-profile design prevents snagging on clothes or gym equipment, allowing you to forget you're even wearing it. Set the perfect placement and tension on the durable elasticated band by simply sliding the buckle until it feels snug. The secure velcro enclosure enables you to quickly remove the sensor to easily wash the band.Optical heart rate sensors work best when they're held securely against the skin. The Coros band is designed to cradle the sensor flush against your arm to prev