as long as it does not get wet.
water filter – again, you can always boil water or make a filter in the wild, but bringing a filter is much faster. i used to use a straw type filter for this purpose. they are small and fit in your pocket or in the outer pocket of your pack. however, they require you to get on your belly to drink from a water source if you do not have a container. they also can be hard on your mouth. mine left sores from the suction. i switched to a water bottle that has a filter built into the lid. it also has 