Sea to Summit Spark Women's Down Sleeping Bag

The Sea to Summit Spark is a women's-specific mummy bag built around 850+ fill-power RDS-certified goose down at a total weight of 1027 g, putting a lot of warmth into a relatively light package. The down carries Sea to Summit's Ultra-Dry treatment, a non-PFAS hydrophobic finish that keeps loft longer if the bag gets damp inside the tent, and a draft tube runs the length of the zip to stop warm air leaking out at the seam. The women-specific cut and full-length zip mean it can be zipped together with the matching unisex Spark to make a double bag for two. The trade-off for the low weight is the 10D shell fabric, among the thinnest used in backpacking sleeping bags, which demands care when packing and around gear with sharp edges - not a bag for tossing loose into a pack next to crampons. No comfort or limit temperature rating is listed here, so match it against Sea to Summit's published temperature chart for your trip rather than judging warmth from fill power alone. It suits backpackers prioritising pack weight who are comfortable handling a delicate ultralight shell.