What Our Gearhead(R) Experts Are Saying: "I used the Helium UL Bivy on a fastpack trip in the Tetons-kept me dry through an unexpected storm and ventilated better than any bivy I've used. The updated Pertex Shield fabric is super light and surprisingly tough, and I love that it's made from recycled fishing nets." For minimalist mountain missions where every ounce counts, we rely on the Outdoor Research Helium UL Bivy to deliver weatherproof protection without compromise. Engineered with 2. 5L Pertex(R) Shield NetPlus(R)-a recycled nylon fabric made from repurposed fishing nets-this bivy balances sustainability with serious performance. It's waterproof, highly breathable, and light enough to disappear into our pack until it's time to bed down under the stars. The 2026 update adds smart features like dual passive ventilation flaps for airflow and condensation control, plus a high-volume toe box that gives our feet space to move and our bag room to loft. The clamshell opening makes for quick and easy entry, and the single DAC pole lifts the canopy just enough to keep the mesh off our face while sleeping. Whether we're weathering a summit push or sneaking in a backcountry overnight, the Helium UL Bivy is our go-to for dependable protection in the lightest form possible.