They're wide mouth, so you can easily store stuff other than water in them. I use one for my larger survival kit in my backpack (in addition to my pocket PSK). With that Nalgene survival kit I know things inside are waterproof, it will float, and I have a container to store water in (after dumping out the contents).

They're wide mouth, so you can put ice in them with your drink.

If you happen to have a MSR MiniWorks water filter, it will screw right to the top of a Nalgene bottle for easy filling.

They have volume markings on the side, so they can function as measuring cups. You can see through them, so you easily know how much water you have left

They don't leak. They last forever. Pretty much indestructable.

The lid is attached so you don't lose it. The attachment is heavy duty, so you can tie a cord to it and then strap it into your canoe.

Most things try to accomidate them. Many backpacks advertise "Side pockets fit Nalgene bottles", etc.

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Downsides - they're wide mouth, so if you try to drink water from them too fast while bouncing around, you'll end up getting a bath. Inserts are available to make fast gulping-on-the-go less messy. They're too wide to fit in standard bicycle bottle holders.

No ... I don't sell Nalgene bottles, I just use them!
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