libbey duratuff cortado / gibraltar rocks glass 4.5 oz libbey this is the same cortado glass used at the top coffee shops all around the country. originating at san francisco's blue bottle, the cortado is a 4.5oz espresso drink with milk textured as a latte. sometimes called a gibraltar, this drink epitomizes the third wave coffee movement. this libbey 4.5oz gibraltar glass is the original and the most popular glass for the drink. with paneled sides and octagonal design, this glass is built for beautiful aesthetics as well as functionality. thanks to a special thermal after-process applied to the top portion of the glass, you can rest assured that it has exceptional durability to match its looks! this duratuff treatment is designed to increase the glass's resistance to mechanical and thermal shock while also making it safer to use.