Mylar Emergency Thermal Blankets (4-Pack)

These are the classic aluminized Mylar space blankets you'll find in first aid kits and go-bags, sold here as a budget four-pack. Each one unfolds to 82"x52" — big enough to wrap an adult — yet folds down small and light enough to forget it's in your backpack until you need it. The reflective foil is designed to bounce back up to 90% of your body heat, which is exactly what you want when cold or shock sets in.

They suit hikers, campers, marathon runners, and anyone building an emergency or storm kit. At under six dollars for four, there's little reason not to stash one in the car, one in the day pack, and keep the rest at home. The material is tear-resistant and technically reusable, though these are best treated as backup gear rather than a nightly camping quilt.