What is Supima? Only the best cotton grown in America! With extra long fibers that feel smoother, take dye better and last longer than lesser cottons. It s rare, too — less than 3% of American cotton is fine enough to wear the Supima name. So you know it makes an exceptional tee.With a flattering boat neck and elbow sleeves, think of this tee as your new go-to.Supima is conscientiously sourced, American-grown cotton that s farmed to minimize environmental impact.