High performance compression shirt with Heart-Gard sewn in. 80-85% Nylon/15-20% Lycra. Heart-Gard is a tough, high density polyethylene dome that absorbs impact energy and forces it away from the heart. It is small in size, measuring 6" x 6", yet is the largest rigid plate over the vital area of any protector. When worn with the compression shirt, it is virtually invisible and does not restrict movement. It is comfortable and cool, so you forget you are wearing it. There is no guarantee or warranty from injury, helps to guard the heart.