The tops of the first two models fit loosely and should not be counted upon to seal the boxes in any way, but those tops will keep out dust and do an acceptably good job of keeping the contents protected

Being weather tight protects the contents from moisture too.

STORAGE AND HUMIDITY:------------------------I tested several common plastic letter/legal storage containers for their ability to protect contents from the usual big humidity swings in many basements (for example, due to

Love the "O" ring like seal.