These files boxes are what I had hoped. They are sturdy and stack well. The lids are not the ultimate in thickness but for the price these are exactly what I need for moving files around from state to state.
Right size for files in folders. Bought it because the sides are straight to stack and store better. Seems ok for that. I won't know for a long time how sturdy it is in the attic.
The plastic file organizers we purchased work great and are high quality. Their stackable and quite sturdy. Much better that my old paper file boxes. We found them cheaper on line (with Staple's) and the store matched the price. My only minor complaint - why do manufacturers apply stickers that are difficult to remove???