EXCLUSIVE AT MR PORTER. Portuguese Flannel's 'Teca' shirt is tailored using techniques honed by four generations of shirtmakers. It's made from cotton - the brand's based in mills around GuimarĂ£es, a northern Portuguese town with a legacy in textiles.Lower Impact Materials. This product is made using at least 50% lower-impact materials or ingredients. Find out more about our Consciously Crafted criteria here.