Gone_fishin's looks like it was made out of either cardboard, or plastic.
Lothar's looks like a "lucky find". I'm guessing that it's sealed with something, maybe silicone. Looks nice, and works great.
Gone_fishin's will be quieter though, because it is always quieter to run multiple small fans, than it is to run a single large fan (given the same cfm).
I'm a proponent of the do-it-yourself-out-of-fiberglass, but all my tools and supplies are in storage right now
