HexoSkin’s biometric shirts measure and interpret performance data for a user, including heart rate recovery, lung capacity, and other signals. Each shirt features two conductive bands, one around the top of the chest and one around the bottom that "make contact with the skin at three points using patches of silver woven into the fabric. These contacts are used to measure the electric potential on the skin generated by electrical signals in the heart. The area inside each band can also be calculated by measuring the strength of the magnetic field within the conductive ring. And by extrapolating the two area measurements, Hexoskin can estimate how a user’s lung volume changes as they breathe. Finally, the data-recording device, which connects to the shirt and fits into a small pouch near the hip, includes accelerometers that track the user’s movement." Additionally, "The battery on the recording device lasts around 14 hours, enough for a week’s worth of training for many people, and the device can store up to 150 hours of data. Users can monitor their vital signs through a mobile app available for iOS and Android devices, and can build their individual fitness profile by completing a series of four tests."