Everyone has pretty much covered it, this is just my additional 2 cents. I’ve frequently back country hiked and/or hunted, so weight is usually at a premium. This summer my brother and I used one of the platypus gravity filters in Colorado between 8-12 thousand feet for almost 40 miles. Absolutely loved it! Gravity feeding will rock your world after using a hand pump system for greater then one person. The only issue I had was it requires a deeper source of water to get water from then a hose. Not a real big problem, but there isn’t a whole lot of water at 10,000+, much less in pools or deep streams. I’d also recommend the carbon filter, it helps immensely with the flavor.