Luciano High Borosilicate Square Glass Food Container With Vent Lid 520ml Make no mistake, this container glass is not like other lock and lock / click and lock glass food containers. It is made of High Borosilicate Glass, which means they can be used in the oven, on gas, in microwave, as well as put in the freezer, and thus it can resist very high and very low temperatures. They are also dishwasher safe. Its cover comes with a vent lid to allow you to cook food in the microwave while the lid is on (vent open), although this is not the best way to use for extra long durability. Also the vent lid allows to keep food wet or dry according to need during storage. These containers are extremely useful because they can be used to cook, and then to store the remaining items in the fridge or in the freezer. The covers are ultra tight to allow good closure and isolation. Other Luciano Containers sizes of the same category are 800ml, and 1200ml. These glass containers are made in China in Luciano Glass Factories. The Lids are bought from a high reliable plastic supplier and guaranteed for food safety.