Sierra Madre Emergency Sleeping Bag - Waterproof Thermal Bivy Sack, 5-Pack Lightweight Reflective Mylar

Built from durable PET mylar originally developed for high-performance insulation, this bivy sack is designed to be a compact, reusable layer of protection for outdoor adventures and emergency kits. Each bag folds down small to fit into a drawstring stuff sack, yet expands large enough for full-body coverage. It balances low weight, windproof and waterproof barriers, and thermal reflection to help reduce heat loss when shelter options are limited.

How does this bivy sack keep me warmer when I’m exposed?

The Sierra Madre bivy uses reflective mylar to send up to 90% of your radiated body heat back toward you, which helps slow heat loss in cold environments. Its windproof film prevents convective cooling from gusts while the waterproof surface stops rain or melted snow from soaking insulation layers beneath.

• Reflective PET mylar returns body heat to reduce chilling.
• Windproof membrane blocks cold air infiltration.
• Waterproof exterior repels rain and wet snow.
• Full-coverage sizing fits most adults for better heat retention.

Can I use this for more than one emergency or trip?

Yes — unlike paper-thin survival blankets, this bivy sack is made for multiple uses. The tear-resistant PET film is rugged enough to be wiped clean and repacked, making it appropriate for planned outings, roadside emergencies, or stored as a reusable survival item.

• Durable PET construction resists tearing and punctures.
• Machine-foldable into provided drawstring sack for storage.
• Light cleaning and drying extend its service life.
• Suitable for repeated inclusion in kits and packs.

How portable is the thermal bivy for backpacks and cars?

Weighing only about 6 ounces per bag, the bivy stows into a tiny stuff sack that fits inside backpacks, glove compartments, or first-aid kits without adding bulk. Its low pack volume and light weight make it an ideal addition to minimalist hiking setups and vehicle emergency kits alike.

• Approximately 6-ounce weight for ultralight carry.
• Compact drawstring sack for tight pack spaces.
• Packs small enough for glove compartment or belt pouch storage.
• Five-bag pack gives multiple occupants or reserves for group use.

What situations is this bivy best suited for?

The bivy is intended as an emergency thermal barrier rather than a primary sleeping system. Use it as an outer layer in hypothermia prevention, an improvised shelter liner, or a moisture shield during unexpected storms and roadside incidents.

• Backcountry hiking and overnight emergency backup.
• Car or home emergency kits for unexpected weather events.
• Preparedness supplies for camping, hunting, or search-and-rescue.
• Group outings where multiple quick-deploy layers are needed.

Who is this for: The Sierra Madre Emergency Sleeping Bag is ideal for hikers, campers, outdoor guides, preppers, and families who want a lightweight, reusable thermal option in their safety toolkit. It’s also practical for motorists and workplace first-aid stations that need compact, reliable protection against wind and wet conditions. Keep it packed and accessible so you have a quick, reflective barrier when shelter or dry clothing isn’t available.