Original spare part. The Polar Soft Strap heart rate belt is the same as the belt supplied with the Polar H9 heart rate sensor. It also works with H10 sensors, with the difference being a different buckle and the lack of interference-reducing extra electrodes in this model. (The H10's Pro Strap has a plastic "clip buckle," while this one has a hook-like buckle through which the other end of the belt is threaded) The strap is machine-washable. Follow the instructions on the packaging for maintenance to ensure the longest possible lifespan for the strap. Tip: Although the instructions recommend wetting the contact surfaces of the strap specifically, it is often more effective to wet the skin on your chest in the corresponding areathe surface material of the strap's contacts repels water quite strongly. The belt is elastic, and enables adjustment between 65-107 cm. Note! This is a spare part belt, and the H9 sensor is not included.