Libbey Duratuff Cortado / Gibraltar Rocks Glass 4.5 OZ 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! The versatile 4.5-ounce size is also well suited to serve double time in the kitchen and bar, eliminating the need for two sets of glassware-simply add the other Gibraltar sizes to handle every serving need. This DuraTuff treatment is designed to increase the glass's resistance to mechanical and thermal shock while also making it safer to use. Dishwasher Safe. Approx size; 133ml / 4/5 oz.