This is a very roomy bag that easily held all my items.  I Just returned from a flight on United and this bag fit easily under the seat in front of me.  My water bottle was easily accessible.  The bag was not completely full, but there was more than enough leftover space to fill the bag to its maximum without a problem.  I placed the heavy items (books, shoes) on the bottom and I was able to carry it on my wheeled carry on bag.  No bag fees and no waiting at the carousel.  My traveling companion is now ordering one for herself.