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What is the Big Agnes Greystone 0° Regular Left Sleeping Bag?
The Greystone 0° is the warmest option in the Greystone series, designed for cold-weather adventurers who need reliable thermal efficiency without sacrificing packability. With nearly twice the insulation of the 20° version, it provides dependable warmth for backpackers, mountaineers, and campers tackling sub-freezing nights. Its contoured hood, oversized no-draft collar, and PFAS-free water-repellent shell make it a trusted choice when temperatures plunge. Whether you're setting out on a winter expedition or camping in late autumn, the Greystone 0° delivers the performance needed to sleep soundly in challenging environments.
What is it made of?
Insulation
At the heart of the Greystone 0° is 600-fill DownTek™ down insulation, with a generous 964g fill weight to provide serious warmth. Down remains the gold standard in insulation for its warmth-to-weight ratio, trapping body heat efficiently while staying compressible enough for packability. Treated with a bluesign®-approved, PFAS-free water-repellent finish, DownTek™ resists moisture absorption, maintains loft up to 90% longer in damp conditions, and dries significantly faster than untreated down. This ensures consistent performance, even in snowy or condensation-heavy environments where untreated down would typically collapse.
Shell
The outer fabric of the Greystone 0° is made from recycled polyester ripstop, chosen for its excellent strength-to-weight ratio and long-term durability. The "ripstop" weave pattern integrates stronger reinforcement threads into the fabric, preventing holes or tears from forming and spreading. This weave makes it more resistant to abrasion and wear from rough ground, frequent packing, or contact with outdoor gear. On top of this, the shell is finished with a PFAS-free Durable Water Repellent (DWR) coating. Unlike traditional DWR finishes that often rely on harmful fluorochemicals, this alternative effectively sheds light moisture inside a tent, such as condensation or drips, while reducing environmental impact.
Lining
Inside, a recycled polyester taffeta lining provides a soft, smooth feel against the skin, enhancing comfort for nights when you're not layering up heavily. This lining also benefits from a PFAS-free water-repellent treatment, a second barrier to protect the down insulation from moisture that might penetrate the outer shell.
Construction
The Greystone 0° uses a baffled construction, a design where the down insulation is contained within stitched chambers. Unlike simpler "sewn-through" designs that can create thin, cold-prone spots, baffled construction allows the down to fully loft within evenly spaced compartments.
Additionally, baffled construction enhances the long-term durability of the bag's insulation. It preserves loft even after years of compression and expansion cycles by preventing the down from shifting or clumping into corners.
What are its features?
Thermal Efficiency
The mummy shape reduces bulk and weight while increasing body heat retention. A contoured hood follows the natural shape of your head, while an oversized no-draft collar, no-draft zipper, and insulated tube along the hood opening seal in warmth.
User-Friendly Design
A low-profile cordlock allows you to uncinch the hood with one hand. The smooth-running 165 cm YKK #5 two-way anti-snag zipper is positioned on the left side, complete with a zipper garage for snag-free operation.
Adaptability
Left-zip all-gender Greystone bags can be mated with right-zip women's models to create a shared sleep system. Interior loops let you attach a liner for extra warmth (sold separately), while exterior loops allow for hang drying or long-term storage.
Packability and Versatility
Despite its heavier insulation, the Greystone 0° compresses to a packable 23 × 30 cm, making it suitable for backpacking in winter conditions. A larger 26L stuff sack (25 × 53 cm) is included for storage and to preserve loft between trips. It works with any sleeping pad, though pairing it with a higher-insulation pad is recommended for maximum warmth in extreme cold.
Comfort and Temperature Ratings
Independently tested to ISO 23537-1 standards, the Greystone 0° provides trusted performance:
- Comfort: -9°C (16°F) — the lowest temperature at which the average woman will sleep comfortably.
- Lower Limit: -16°C (3°F) — the lowest temperature at which the average man will sleep comfortably.
- Extreme: -38°C (-36°F) — survival rating for an average woman.
Features:
- Warm mummy-style design with maximum insulation for cold conditions
- 600-fill DownTek PFAS-free, water-repellent down
- Generous 964g fill weight for dependable warmth in winter
- Recycled polyester ripstop shell with PFAS-free DWR finish
- Recycled polyester taffeta lining with PFAS-free DWR finish
- Contoured hood with low-profile cordlock for one-hand adjustment
- Oversized no-draft collar, draft tube, and zipper garage for superior thermal protection
- YKK #5 two-way anti-snag zipper on left side
- Liner loops and exterior storage loops for adaptability
- Mateable design (left + right zip bags) for two-person use
- Stuff sack and storage sack included