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I bought this as a dirty bag for a 3 person group, we generally hike the AT 3 to 10 days at a time. being able to collect a large amount of "dirty" water, and bring it back to the camp to filter and use was a primary concern for me. I like that this is a "pre-filter" before getting to my gravity filter, as it helps the life cycle of the primary. a couple quick connect mods and this has been great