I am using it for preserving seaweed. The airtightness is high and it is safe. Korean seaweed was in trouble keeping it longer than Japanese one, but if it is this it will fit in it. It is goods you bought.
I was looking for a case that was excellent in air tightness (packing etc.) about 5L. I could not find anything that favored hope, but I finally found it on this site. Actually I bought it to make handmade miso. It is safe to put the 5L miso so it will be fine.