Math Humor Shirt - Come To The Dork Side, We Have PI (PIE) Solid colors: 100% Cotton; Heather Grey: 90% Cotton, 10% Polyester; All Other Heathers: 50% Cotton, 50% Polyester Imported Machine wash cold with like colors, dry low heat Lokira's Closet Math Humor Shirt Lightweight, Classic fit, Double-needle sleeve and bottom hem