The screw-on mechanism ensures an airtight seal which will prevent air to enter, protecting the hermetic seal of the jar. Airtight canisters not only protect the contents from insects and moisture, but also ensures they remain fresh for a long time. They are great for storing cookies, coffee, flour, sugar, nuts, coarse cereals and more. These stainless steel kitchen canisters are dishwasher-safe, however we recommend hand-washing to protect the finish. A quick wipe with a damp cloth is sufficient for a light cleaning. Clear see-through window allows easy viewing of canister contents. With transparent glass window, you will save more time.