Do consider buying a K&M matchcase specifically designed to house the REI matches. Yes, they are a bit pricey, but they are rock solid, 110% waterproof, you only need one (or two?), and they'll last several lifetimes.

http://kmmatchcase.safeshopper.com/

Note: it appears that they are out on a bit of a vacation right now, but they'll be taking orders again next week.