4th - luckily at the exchange on base it is only $99 instead of the $139 at other places. I have a katadyn combi filter I keep with my backpacking stuff and a MSR inline filter for my camelbak.
Even though I have filters i keep eyeing up the MSR Miox as another alternative (since it is a purifier not a filter).
"To show you how radical I am, I want carjackers dead. I want rapists dead. I want burglars dead. I want child molesters dead. I want the bad guys dead. No court case. No parole. No early release. I want 'em dead. Get a gun and when they attack you, shoot 'em."
Ted Nugent - speaking at the NRA convention April 17, 2005