Fresh Keeper 37-Piece Container Set with Blue Lids and Lid Organizer Airtight, "burpable" seal to preserve freshness during storage Date-set feature to track food storage time (simply align lid pointer with date on container rim) Heavy gauge plastic for durability Includes lid organizer to organize and store up to 20 lids in a small space Microwave safe, freezer safe, dishwasher (top rack) safe, BPA-free and made only in USA