Adult sizes are softstyle:
4.5 oz./yd² (US) 7.5 oz./L yd (CA), 100% ring-spun cotton, 30 singles
Softstyle's high stitch density, soft ring-spun cotton and cotton blend fabric 
Modern classic fit 
Youth sizes are heavy cotton:
5.3 oz./yd² (US) 8.8 oz./L yd (CA), 100% cotton, 20 singles
Classic fit