Thermoglass Baking Dish is made from premium heat-resistant borosilicate glass making it strong and oven safe. The dishes, without the lids, can be used in a conventional oven. The real seal lid, which has a steam/air release vent, allows use of the Thermoglass dishes in the microwave for convenient cooking and reheating. The soft silicone seal in the lid makes the dishes airtight and leakproof, so prepared meals or leftovers can be stored in the fridge and freezer.