Just a tad narrow -- by an inch or so -- and doesn't accept folders very well but with some coaxing it'll do. Best part is how light the box is and doesn't increase too much with contents. I suggest it's great for folks like me with thumb arthritis. (that's thumb not some)!
This box seems sturdy enough for all the paper I'm stuffing into it and I like that the rails enable either letter or legal size hanging file folders. I was able to place an oversized item along the bottom underneath the hanging file folders as well and to place some other flat oversized items (like large wall calendars) on top as well. The lid stays on and this helps me stay organized. I like that I can see into the box without it being totally clear.