On a long tour day, the bottom of the pack holds the gear nobody hopes to use, and the ARVA Lite Bivvy is the emergency bivy sack that earns its spot by being easy to forget. It is windproof and highly water-repellent, though not waterproof, and the brand says it reflects up to 70% of body heat. It also works as a sleeping bag cover or a standalone summer sleeping bag, so this lightweight bivy sack can pull duty well beyond emergencies. What Our Gearhead(R) Experts Are Saying:"After a night out, the inside stayed drier than I expected, because the material breathes and moisture escapes instead of collecting on the walls. That is why it has a permanent place in my pack: I can wake up dry enough to keep moving instead of starting the day wet."