Down filling has the greatest warmth-to-weight ratio of any insulation, but it has a fatal flaw: It fails when wet, making many active folks turn to winter jackets and sleeping bags with synthetic insulation. By utilizing a new waterproof-treated down insulation, the Sierra Designs Zissou 15 (rated to 15 degrees F) solves this issue. It's also one of the best sleeping bags in recent years. We spent significant months testing it in such areas as the always-wet Olympic National Park rainforests, and the trim, yet comfortable bag never failed to keep us dry and warm. [$260; sierradesigns.com]
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