From the TrueSeal Kitchen Storage Collection. TrueSeal containers offer versatility to prep, bake, transport, serve and reheat. These tempered glass containers are oven, microwave, dishwasher, refrigerator and freezer safe. The lids are designed to prevent spills and leaks with clear view windows for viewing what's inside. Tempered glass containers may be used in gas and electric ovens up to 425°F, or microwave ovens without browning element. The lids are intended for microwave use only for reheating purposes, and storage in the freezer and refrigerator.