Myself, I can't have anything with Iodine in it. Iodine won't kill me but it could do a lot of damage to my thyroid due to a previous thyroid condition. So I have been using the Katadyn Micropur MP-1 anyway and they are great. There is the very slighted taste of chlorine in the water but that is it. I'm talking about a very slight taste. I have actually tasted tap water in some areas with more of a chlorine taste to it. The fact that they are very well packaged is a big plus too. I keep 2 in my wallet, 6 in my PSK and 12 in my car kit. I always take them when I go camping/hiking and I have used them to purify some very questionable water and have not gotten sick yet (knocking on wood). I use them in conjunction with a chemical-free activated charcoal bottle filter and in 30 min all the nasties are dead. The filter takes care of the bacteria-based nasties instantly, which leaves the MP-1's with only the job of having to kill viruses, which they do quite quickly and efficiently.
Okay sorry for going a little off-topic there. About these vials... I have been looking for some for storing a few days worth of prescription meds in. These things are so cheap that I think I'll buy a couple of each and see how they work out. I'll keep you guys (and girls) posted.
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Learn to improvise everything.