Personalized Pi Day March 14 Math Lover Science T-Shirt. Whether you're attending a math-themed party or just want to express your geeky side, this Pi Day apparel is a must-have. Grab yours today and wear your love for math proudly! 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.