The suunto ant comfort heart rate belt is made from soft materials and has traction strips and adjustable buckles to secure the monitor in place and keep it comfortable at all times the device provides very accurate real time heart rate readouts and is compatible with suunto ambit ambit2 ambit2 s ambit2 r watches and suunto m4 m5 quest t3 t4 t6 heart rate monitors it uses disturbance free ant technology for great results and has a user replaceable battery and weighs 42g 15oz