Some old-time Yankee ingenuity here: I bought these refills to place inside tin containers I have been storing flies in. Running out the door one day, I didn't have time to set up my floating fly boxes. I just grabbed the tin. It has been in my vest ever since. Floating fly boxes are nice, but you can make a lot of less-expensive ones with this material and a few old hinged candy or tea tins. The backs are super-sticky, so all I had to do was measure and cut.
Now your rusty little old Altoids tin can be a good fly box. This foam is the real deal--just cut and install, and any likely container you might want to use becomes a useable fly box. Also handy if you've lost that little patch of sheepskin to dry your flies on. Pop a piece of hook'n'loop tape on the back of the foam, put a matching piece on your vest/jacket/wader pocket and you're good to go.