Enough space for a week long trip to the Green River fits everything from midges, nymphs, dries, terrestrials to moderate size streamers. Clear lid helps finding flue before opening since it is two sides. The Zerust is nice to to have as added protection if moisture happens to get into box which is almost every trip especially in the rain and snow although you should always dry out the box at end of day when you get indoors anyway by opening up both sides to make sure the flies are dry and never put used flies back into box without being 100% dry. The watertight seals is nice to have just in case you happen to take a dunking. The only negative is the weight of the box due to the rugged construction/plastic used in it's construction or this can be a positive because the fly box is so robust. I would not take these on an extended backpacking trip due to the weight and would opt for a lighter option. I have four of these to be used specifically for the different waters/locations I fish so I can grab and go and know that I have a good selection of flies that will work.