These platy bottles are excellent. One of those rare AWESOME additions to the backcountry arsenal. I wouldn't have tried a "Folding" bottle unless a friend had used them a lot and loved them. They are counter intuitive - it seems like they'd crack or wear, folding and scrunching them. Not so. They weigh 1/8th of a nalgene liter bottle, for the same volume. Excellent way to have extra capacity on a hike or backcountry trip. I use an MSR water filter, so I carry only one nalgene to pump into (the pump fits on that size mouth), then empty a bottle at a time into the Platypus. When they're empty, I roll them up and they take up less space than a cany bar. In very cold temps (single digits), the small opening may freeze and fill with ice, but this is easy to deal with compared to other bottles - the lid material is thin but durable, and if you hold it in your hand a few seconds, it will release, and you can get the lid off. Just dip the opening, now, in hot water (while cooking) and the ice "plug" releases. Excellent product.