For water treatment, I prefer SteriPen's Adventurer—provided you learn how to use it and have a backup plan. If you insist on carrying a microfilter, MSR's Hyperflow is the lightest, but the Katadyn Hiker is easier to use.
If you don't use a bladder, stick with Nalgene's classic HDPE wide-mouth bottle, which is by far the safest available plastic. Ultralight hikers can and do carry water in the ultralight packaging you get in grocery stores, but be aware that is a relatively fragile option.
Filters & Water Treatment
- Steripen Freedom
- Platypus Cleanstream Gravity Filter
- Katadyn Hiker Microfilter
- MSR Hyperflow Microfilter
- SteriPEN Adventurer