Compatible with chest strap suitable for heart rate measurement with certain brands. The smart combination of soft fabrics and adaptive electrodes makes it extremely sensitive. Being an indispensable part of heart rate monitors, it will accurately detect and transmit your real-time heart rate to a smartphone. The most popular heart rate belt in the world is easy to use yet highly durable. Utilizes the snap attachment method. Color: Black. This lightweight garment is compatible with all heart rate sensors (ANT+, Bluetooth 4.0, 5.3K). With the chest strap made from high-quality material, it can be attached closely to your skin, allowing heart rate sensors to detect your heart's electrical signals more quickly and accurately. Material: Silica gel + fiber. Belt length: 90-130cm / 35.4-51.2in. Package Included: 2 x Adjustable Elastic Strap. Only the above package content, other products are not included. Note: Light shooting and different displays may cause the item's color in the picture to differ slightly from the real thing. The allowed measurement error is +/- 1-3cm.