The NEW Polar WearLink Transmitter Heart Rate Sensor in size M-XXL is a reliable and versatile heart rate monitor suitable for both indoor and outdoor activities. With a battery life of more than 7 days, this unisex adult device provides accurate heart rate measurements in both decimal and imperial units. The sensor comes with a chest strap for secure attachment and is made of durable nylon and plastic materials in a sleek black color. Compatible with Polar brand heart rate monitors, this unit is a must-have for gym and training sessions.