I just bought the steripen travelor at Costco for $49. It comes with 4 lithium batteries and weighs 6 ounces with 4 bats in it. It has a nice water bottle with a prefilter and the steripen sits in the top of the prefilter, and reaches into the water bottle. Around here the water comes mostly from gin clear mountain streams and no filtering is required. Since it only weighs 6 ounces and can refill a canteen with heavy water, it has a place in hiking in mountains with streams. Maybe the worst thing to filter out around here is glacier silt. I cannot taste any taste from the steripen and though I try not to look at it, there is really no safety warning about the UV light.
Jim