Comfortable chest strap for heart rate measurement compatible with Polar, , products. The smart of soft fabrics and adaptive electrodes make it extremely sensitive to Being an indispensable part of heart rate monitor, it will detect and send your real-time heart rate to the smart phone accurately. The most popular heart rate belt in the world easy to use yet is very durable. Utilizes the snap attachment method. Color: Black This light garment is compatible with all heart rate sensors(ANT+, Bluetooth 4.0, 5.3K). With the chest strap based on high quality material, it can be attached to your skin closely. your hearts electrical signals, so the heart rate sensor can pick up your heart rate quicker and more accurately. Material: Silica gel + fiber Belt length: 90-130cm / 35.4-51.2in Package Included:20x Adjustable Elastic Strap Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.