I use a MSR miniworks HP filter. It's all user serviceable, and has a reasonably priced ceramic filter($40). I believe its a .2 Micron, with a .3 Micron max. The filter can also be cleaned with the included abrasive pad to help with flow problems. It screws directly onto a nalgene bottle or bottles with similar threads. I have had it five or so years and it has probably seen about 800-1000 gallons over 100+ backpacking trips. It's a little slow and requires a bit of effort, but its proven itself to me. It's also very durable, but the ceramic filter inside, like all, is not hard to damage, but when rolled up in my sleeping bag in my backpack, it did survive a fifty foot drop onto rocks below.

Important note: you MUST NOT let any ceramic filter element freeze, especially when wet, this will create tiny cracks and render your filter useless.

Edit: this is more of a fast and light travel set up.

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