Details from Nordstrom website: “Contrast piping outlines classic menswear-inspired knit pajamas that pair a button-up top with soft, fluid pants to complete the set. Top has notched collar; long sleeves 91% Tencel® modal, 9% spandex Tencel modal is a sustainably produced fiber made with closed-loop processing and is certified with the EU Ecolabel as having a low environmental impact throughout the entire lifecycle”