Built to tackle truly frigid conditions, the Marmot Datum is rated to -18° by blending efficient synthetic insulation with the pure warmth of water-resistant, 650-fill-power down.

• Body-mapped 650-fill-power down with Down Defender resists moisture and wraps around body, head and feet; super-efficient Spirafil synthetic insulation fills the bottom
• Body-mapped insulation yields maximum thermal efficiency without added weight
• Full-length, locking YKK 2-way zipper
• 3D hood construction
• Internal stash pocket
• Antisnag insulated draft tube
• Closeout
• Imported.
• Many sleeping bags are rated for temperature by an independent testing protocol. With both European Norm (EN) 13537 and International Organization for Standardization (ISO) 23537 testing, each bag gets a Comfort (or T-Comfort) rating and Lower (or T-Limit) rating. The Comfort/T-Comfort rating is the lowest temperature at which the bag will keep the average cold sleeper comfortable, and the Lower/T-Limit rating is the lowest temperature at which the bag will keep the average warm sleeper comfortable. Ratings are based on a person wearing one long underwear layer and a hat, sleeping on a single 1 in. thick insulating pad. Many brands use the Comfort rating for women's bags and the Lower rating for men's and unisex bags. Everyone's body and sleep comfort differ, so EN and ISO ratings are simply a guideline to help you compare products.