Remember there is a big difference between a water FILTER and a water PURIFIER.

We don't have a water purifier in our emergency preparations, but our "bug out bag" water filters are:

* Aquamira Frontier Filter (very small and lightweight unit that can be carried virtually anywhere. The Frontier is rated for roughly 20 gallons. The Frontier Pro is rated for more. The Pro can be used a "suck through" or "gravity" filter while the base model is an idiot proof suck through unit. We have these stored in a small on-body survival kit).

* Katadyn Hiker (Lightweight pump filter. My wife has this unit in her BOB. We selected it based upon my experience with Katadyn products, and its light weight. It is not, however, built overly durable. Roughly handling could result in a broken handle).

* Katadyn Pocket (Heavy duty pump filter rated for 13,000 gallons with a ceramic element. This is my BOB filter. I bought this unit before the Y2K scare, and if memory serves it was over $200 back then. I think they're around $230-250 now. This is the "Rolls Royce" of pump filters).

The small "straw" type filters are great for PERSONAL SURVIVAL KITS, but I'd supplement those with a higher capacity pump filter for my 72 HOUR KIT.