Platypus GravityWorks Filter and Purifier System - $119.95

When you come around a bend in the trail and find someone crouched in the mud, grunting and pumping furiously, your initial thought is usually a little disturbing. The Platypus GravityWorks Water Filter and Purifier System cleans four liters of water in 2.5 minutes with no pumping and very little grunting required. Just fill the dirty water reservoir and hang it above the clean water reservoir. Gravity will take care of the rest. - $119.95