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The Terra Nova Ultra Bivy Bag is the ultimate shelter for fastpackers and weight weenies. The Ultra Bivy packs down to just 3 by 4 inches and weighs only 2 ounces. You won't even know it's there until you need it.

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Is this waterproof or DWR? What is the...

Is this waterproof or DWR? What is the material? At 2 oz, I would consider adding to my tarp setup to provide a bit more protection to my sleeping bag from rain splatter.

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Ultra is what's called a cuben fiber. Doesn't breath at all, so what you make up for in moisture from rain splatter, you get back in internal condensation. Here's the scoop on cuben:

Cuben Fiber:

Cuben Fiber is a high-performance, non-woven, rip-stop, composite laminate developed in the 1990s by a nuclear weapons physicist and an aerospace composite engineer. Originally designed for use in world-class sailing, it is ideal for certain applications in lightweight and ultralight outdoor gear due to its unmatched strength-to-weight ratio.

Technically speaking, Cuben fiber is a laminated fabric made using patented technologies with unidirectional prepregnated tapes of in-line plasma treated fibers that are spread into mono-filament level films. In more simple terms, Cuben fiber is made by sandwiching Spectra or Dyneema polyethylene fiber filaments a thousandth of an inch thick, in various arrangements between thin outer layers of polyester film. The ?sandwich? is then melded together in a high-pressure autoclave.

Cuben fiber is lightweight, highly durable, and is 50-70% lighter than Kevlar, four times stronger than Kevlar, and allows flex without losing strength. It is also less than half the weight of silnylon, has low specific gravity (floats on water), high chemical resistance, excellent UV resistance and is 100% waterproof.