Spacious, easy to access and good venting make this lightweight bivy a great all-rounder. Sierra Designs says Updated With New Color & Styling. Still designed to fit our revolutionary Backcountry Bed and a 2.5” inflatable pad on the inside of the bivy, so you can sleep as comfortably on a rock ledge, as you do at home. Our Verdict Sierra Design's Backcountry Bivy uses an interesting design to increase space and comfort. The simple, unstructured design minimises weight while the use of a thicker floor fabric ensures durability is not sacrificed. There is a good amount of internal space which allows you to move around easily enough, even with a thicker mat and bigger sleeping bag. The bag uses two different U-shaped openings, one for access and the other for ventilation. This smaller vent opening has a mesh cover to provide protection from bugs. The Backcountry does well for dealing with moisture/condensation with fairly breathable fabric combined with the vent.