100% cotton

from the spirit Jersey website

Use this size guide as a reference to help you to work out your Spirit Jersey® sizing, the measurements relate to our classic crew neck style which is based on unisex t-shirt measurements with a tad of extra room in the body. Men and people with larger builds should size based a normal unisex t-shirt size. Women and people with smaller builds should size down if they're looking for a more classic fit. (If you normally wear a small t-shirt, order an x-small)