Everyone has there own way to store their flies. I throw large 10+ inch flies that are tall, long and thin like a real minnow. Very few boxes are large enough to hold them. None of which will even fit in my chest pack. I sell the flies in these neat little plastic sleeves, which cost around .08 each. I also carry them on the water in these as well. The flies come out of the bag in the nice flat way they should be fished. Most flies out of boxes tend to get squished and bent. I can also put 30-40 flies in the area of a VHS box or the average medium fly box. Another advantage is no extra weight, nor stiffness to the chest pack from the box. I have also found these bags to work nicely in carrying 3 size 6-7 ring cigars. Bonus!