Personalized Pi Math Day grunge T-Shirt. Pi Math Symbol T-Shirt - Black has fun grunge look. graphic licensed from and c. www.graphicsfactory.com Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.