With vacuum-sealing lid technology, these TrueSeal glass containers rated a perfect score for airtightness by the Good Housekeeping Research Institute. Anchor Hocking TrueSeal lid technology features compression-style lid for airtight freshness and spillproof storage. Thick-walled, American-made tempered glass heats food in the microwave, stores food in the refrigerator or preserves pantry staples. Audible and visual proof of the food-preserving vacuum: pressing center releases air -- lid stays recessed. Pliable lids secure to bowls and remove easily. Clear glass to quickly view contents. BPA-free. TrueSeal lid technology earned a perfect score for airtightness by the Good Housekeeping Research Institute. Anchor Hocking is a premier American manufacturer of glassware, serveware, ovenware and storage containers since 1905