Louis,<br><br>No first hand experience with it, but I did research it several months ago and it appears that it does what it claims. There might be some question about oocysts, specifically cryptosporodium parvo (sp?), IIRC - those are tough rascals - but (IIRC) it does better than chemicals against them. Filtration or floculation + filtration is best non-boiling defense against oocystic critters from what I've researched...<br><br>The UV pen appears to do very well on everything else, and of course it (UV) is used for sterilization of municipal water in SOME places (it's expensive at the municipal level).<br><br>HTH,<br><br>Tom