Solid colors are 100% Cotton. Heather Grey is a blend of 90% Cotton and 10% Polyester. Dark Heather and Heather Blue are a mix of 50% Cotton and 50% Polyester. Alternatively, Dark Heather, Heather Blue, and all other Heathers consist of 65% Polyester and 35% Cotton. Girls' Heathers are made up of 60% Cotton and 40% Polyester.