When I don't want to carry my whole gear bag, these are great for the bare essentials. Even when I do need my gear bag, the BDU is compact enough I just slide it right in, as is. It really helps keep my stuff organized. I fit five pens, including the previously-reviewed 0.18 mm pen, a Moleskine planner, Sony Clie PDA, ID and credit card, pocket knife and a small flashlight.