These vintage containers are designed for storing food in the freezer or refrigerator and then reheating it directly in the microwave. Vented Seal: The lid includes a distinctive silicone valve (often pink or red) that allows steam to escape during reheating. Material: Made from durable, heat-resistant plastic suitable for microwave use. Design: These bowls typically have footed bases for even reheating and stay-cool handles for easy handling. Versatility: They are dishwasher-safe and designed for various food storage needs. New old stock. Never been used.