Flat Stacks space saving collapsible storage containers save on valuable kitchen space! These versatile colorful containers collapse flat for easy stacking when not in use. Available in a variety of sizes, shapes and colours to answer your food storage needs at home, on the go and for any occasion. Store leftovers in the fridge, freezer or pantry and when the leftovers disappear, simply collapse the container down for convenient storage in a cupboard or drawer. Flat Stacks SAVE up to 60% of space, are microwave, dishwasher and fridge/freezer safe as they are 100% BPA Free (100% safe for your family). They also come with matching valves on the lids so you are not left searching for a match in your cupboards! (Product Care) The seal on my lid comes out in the dishwasher. The seal in the lid, does come out for cleaning purposes. If food was trapped under the seal and it was not removable there would be a potential for mold to build. We would suggest removing the seal prior to placing the lids into the dishwasher to ensure they are not lost or damaged. When replacing the seal ensure the seal is inserted on its narrowest side. My lids seem to be warping? Always use the top rack of the dishwasher if you choose not to hand wash this product. This will prevent the lid from becoming too hot and changing shape.