Shock Doctor Men's Shockskin 3-Pad Short Sleeve Impact Shirt Constructed with four-way stretch, fabric that wicks moisture away from the skin The integrated fabric and vented foam pads move and contour with the body for ultimate comfort This short sleeve shirt has three integrated ShockSkin and Shockskin contour protective pads on the ribs and spine Four-way stretch mesh down the back and sides for maximum breathability and range of motion Measure chest circumference starting from just below armpit and then across the center of the pectoral muscle. Sizing as follows XS: 30-33 inches, S: 33-36 inches, M: 36-40 inches, L: 40-44 inches, XL: 44-48 inches, XXL: 48-52 inches