(s#22) Brand new in Sealed Blister Pack.. The Polar T31 Chest Transmitter Heart Rate Monitor is a reliable and accurate tool for monitoring your heart rate during gym and training sessions. With a comfortable elastic strap and a sleek black design, this medium-sized unit is suitable for unisex adults and provides measurement for heart rate, time, and calories. The transmitter is powered by batteries and made of durable plastic and acrylic materials. It also features a chest strap for easy and secure attachment to the torso. With multiple language options and a reputable brand like Polar, this heart rate monitor is a valuable addition to any fitness technology collection.