I am looking for some educated/experienced opinions on Puritabs. Before anyone attempts the suggestion let me preface this with the fact I can not use iodine for medical reasons so lets not even go there. So far, to date, I have been using MP-1 tabs with great success, however recent events have required that I find something that packs down smaller than MP-1 tabs. From what I understand (please correct me if I'm wrong) puritabs are very very tiny (about the size of those little nitro pills that people with heart trouble carry with them) and still treat one liter of water per tab. My questions are these. How well do they work? What will they (or wont they) kill? Why are they banned in the USA? What is the down side of using Puritabs? I assume there must be a down side or we'd all be using them instead of AP and MP-1 tabs....right? If someone knows of an article on this or any other website which I missed that would answer these questions, please feel free to simply point me to it instead of hasseling yourself with a lengthy explanation. Thanks guys (and girls)!!