I use manila folders inside hanging folders. When I put the lid on the box the tops of the manilla folders get bent down. It would be nice if there was more space above the hanging rails to accommodate the folders.
These seem to be the only 4 pack available on Staples and they are sold at a good price. They seem sturdy. We are using them for file storage. We stick a "Label of Contents" on 2 sides which may be necessary if you're storing files like we are. They can be stacked and seem to hold a bit of weight when stacked 8 high but it's probably safer to stack 4 high. There's always an issue with lids cracking no matter the weight but if you reinforce with good heavy duty tape the second you see a crack the lids seems to hold up again.