I usually carry around 6 pens and pencils on the inside. In zippers, a 6 inch
ruler, a stick eraser and white out. It holds everything I need very
comfortably. If you need more than that, it does get a bit bulky like other
reviews said (max might be around 14 pens/pencils on the inside). You could keep
highlighters, markers, and pens/pencils in more than one of these instead of
carrying everything in one big case, which I might do myself. I really like its
sleek and simple design, and especially the snap buttons (velcro is loud). For
my purposes, it's perfect.