Buying this Camelbak Arete 18 is like getting two bags in one. For a quick hike, you can pack up 1.5 liters of water and any other essentials you might want to bring. For longer trips, you can flip the whole bag inside out and it becomes a larger water reservoir that you can then put into a bigger bag. Today’s price of $48 matches its all-time-low, just in time for any summer trips.