Personalized Happy Pi Day School Math Party Newborn Layette. Happy Pi Day Newborn Layette - White math teacher or student apparel. 100% combed ringspun cotton 5.8 ounce 1×1 baby rib sleeper. 3/8" flatlock binding at envelope neck and cuffs. Back sleeve flap to protect hands. Elastic opening at bottom. Infant: 0-3 Months