Pi design on men’s t-shirt. It’s made of a thicker, heavier cotton, but it’s still soft and comfy. And the double stitching on the neckline and sleeves add more durability to what is sure to be a favorite! • 100% ring-spun cotton • Sport grey is 90% ring-spun cotton, 10% polyester • Dark heather is 65% polyester, 35% cotton