This one I made for myself, quite spontaneously, to keep my designs in. It just wraps around an A5-sized notebook. It feels very heavy in the hand, looks rugged and inspiring.
The other one was a more conscious effort; it has steel binders built in so you can easily add/remove pages from it. The cover itself is hard so you can easily write on it when you’ve turned the first page over (something that is not very convenient with the first design). It also can be securely closed to keep all the monsters inside. If you happen to have any.