Emergency Water Filter Straw (70050) The world's simplest and most compact "Water Filter Straw." Just attach the expandible straw to the filter, submerge the filter end into the water source, and drink through the straw. The Frontier Filter is tested to trap 99.9% of harmful Cryptosporidium, Giardia and other pathogens. One unit will filter up to 20 gallons (75L) of water. This is the ideal alternative to heavy, bulky and expensive pump filtration units when space and weight are primary factors (such as in your 72 hour emergency kit).