This is an official Marvel studio licensed T-shirt, with the silk-screened logo area weathered to look like Captain America's battle-scarred shield.  Unlike normal heavy duty cotton t-shirts, this tee is soft & light, which makes it breathe better and great for summer.  It's also slightly stretchy, which gives it a more fitted look, as opposed to loose and boxy like ordinary tees.  I'm a size 38/39 chest, and I normally wear a size Medium tee for relaxed fit and size Small for when I want a more form-fitted look.  This tee feels more like a 'smaller-sized' Medium.  That is, it fits like a size Medium, but hugs the arms and torso comfortably like a size Small.