Platypus Water Bottles

One of the favorite pieces of gear among fanatic gram counters are the Playtpus water bottles, made in Seattle.
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These bottles, unlike those omnipresent Nalgene bottles you can see on university campuses, are made of a soft, tasteless plastic. When full they form a shape fairly conducive to holding and drinking, although when near empty they can flop around a bit if you don't control your water flow carefully. When empty, the bottles squish flat and fit damn near anywhere. Alternately, you can roll them, as I do, to fit one into my little day bag around town. I fill it up at work, use it, then empty it and carry it home. A 1L bottle weighs 28g, and although a wider opening would make cleaning easier, you can't beat the weight. (well, you can, with cheapass plastic pop bottles, but they last less time and can't be flattened). My only real issue is with the pushpull caps. These caps are made so that they don't open accidentally in your bag - fair enough - but they are really hard to open, especially with your teeth (not recommended). Still, they are the only bottles I use when I am not boiling water for health reasons.