Survival Outdoor Water Filter StrawSurvival Outdoor Water Filter Straw Mini Filtration Purifier: 1 Its function is to remove large particles, as well as small impurities such as residual silt and rust, while retaining beneficial mineral elements. 2 Multi layer structure filter and straw design, you can put outdoor water into the bag or directly filter the water for drinking. 3 The ultrafiltration membrane with a filtration accuracy of 0. 01 m can filter 99% of harmful substances in the