C&F Design magnetic 3/3 box is unavailable here in the states. I purchased two of these in Japan back in 2005. I had completely forgot I had them as I have not done any steelhead or salmon fishing in several years. The case is designed for medium sized wet flies (size 4-8). On each side it contains 3 rows of 5 magnetic holders. In the center is a divider that holds a dropper wallet on each side. The case is an ordinary s-sized C&F case.
Although unique, the dropper wallet is something I've yet to completely figure out. I can not seem to make it work properly. The theory is you can pre-rig a dropper for fast and easy set up.
The magnets are strong and hold the fly very firmly. With the case open I have shook it violently to see if I could pry a fly out it place and could not.