EFFECTIVE – The GravityWorks Filter removes particles down to 0.2 microns in size, including giardia, salmonella, and cryptosporidium. That means no floaties, sinkies, or swimmies – just clear, safe drinking water. We used the GravityWorks to filter water from hundreds of gnarly water sources on the Continental Divide Trail, and we were always very pleased with its performance. It can render a slurry of muddy, green, or cow patty-infested liquid into clear, nearly tasteless water. We’re impressed!