65% polyester. 35% cotton twill. 7.2 oz. Button closure. Classic collar. Short sleeves. Flap chest pockets with button closure. Straight hem. Square Carhartt WIP label. The Master Shirt from Carhartt WIP is a summer must-have. Perfect for trips to the beach or sunny days around town, the short-sleeve button-up is made from a poly-cotton blend fabric that is lightweight and breathable. The style is directly inspired by American service station attire from the 1960s, featuring two flap chest pockets and a straight hem.