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.