The Mountain Hardwear 1st Dimension sleeping bag is a 30F (-1C) synthetic bag that is flexible enough to be used in both warm and cold conditions. The bag features Mountain Hardwear's Quantum expander, allowing you to stay zipped for warmth or unzip for an extra 8 inches of room and greater ventilation. An alternative to down, the 1st Dimension's Polarguard Delta is a durable, lofty continuous filament insulation.