SteriPEN® is the only portable water purifier that uses ultraviolet (UV) light to destroy waterborne microbes. Whatever your source, SteriPEN purifies clear water by destroying viruses, bacteria and protozoa, including Giardia and Cryptosporidium, in seconds. It's the fastest route to pure, safe drinking water anywhere.
http://www.ukclimbing.com/gear/news.php?id=970