Personalized Pi Day Math Party Buffalo Plaid T-Shirt. Funny Pi Day symbol for a school math party or just to celebrate a love of Pi 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.