Personalized Happy Pi Day Math Lover Party Toddler T-Shirt. Pi Day math themed Toddler T-Shirt - Black has pi symbols in a pie. Fun gift for a geek, math teacher, college math major or any math lover. A toddler-soft cotton tee in look-at-me, big kid colors. 4.5 oz., 100% combed ringspun cotton. White is sewn with 100% cotton thread. Topstitched rib crew neck. Double-needle stitched sleeves and bottom hem. Shoulder-to-shoulder taping.