What Our Gearhead(R) Experts Are Saying:"I've used this prefilter with my Nalgene on countless backpacking trips, and it's a must-have for any backcountry water treatment system. It removes debris like sediment and particulates, so I can use my SteriPEN or other purification methods without clogging or hassle."When we're trekking through the backcountry, clean water is a priority. The Wide Mouth Bottles Pre-Filter from SteriPEN is a handy companion for anyone relying on wide-mouth bottles like Nalgene for hydration. This clever tool screens out debris and sediment, ensuring our water is prepped for purification. With its 17-square-micron filter screen, this prefilter is perfect for creating clear, particulate-free water before using the SteriPEN Water Purifier or other methods. Designed for adventurers, it's lightweight, easy to use, and a practical addition to any backpacking setup.