When a squall pushes across a ridge, the ARVA Pro Bivvy goes on as a poncho first, with arm and leg openings and a hood that cinches down on two drawcords, so the party keeps moving instead of digging for shelter. If the day ends out there, this emergency bivy sack slides over a sleeping bag as a wind and weather layer with taped seams, or goes inside one as a liner. The insulated pack-away cover finishes the job as a seat pad for long waits. What Our Gearhead(R) Experts Are Saying:"I wore it as a poncho on a long traverse and expected to soak through from the inside, but the fabric let moisture escape and the layers underneath stayed dry. The same thing happened when I used it as a liner for a night out, because moisture left the bag instead of settling in the insulation."