If you're counting grams, but still count on a great night's sleep, the Spark may be the right bag for you. Filled with RDS-certified 850+ fillpower goose down treated with a non-PFAS Ultra-Dry Down treatment, the Spark is constructed with a technical hood and zipper draft tube to retain warmth. Comfort comes from a super-breathable 10 Denier liner fabric, while a 10D shell with a non-PFAS DWR plus a highly water repellent hood and footbox fabric shed wind and condensation. The full-length zipper models can be zipped to an equivalent Women's Spark for comfort that couples can share Features RDS-certified, 850+ fillpower goose down with a non-PFAS Ultra-Dry Down treatment for maximum thermal performance Ultralight, breathable 10D nylon liner and a 10D shell with non-PFAS DWR keeps the hood and footbox highly water resistant Technical hood, anatomical footbox and an ergonomic mummy shape - ultralight doesn't have to mean ultratight YKK #5 zippers with zipper plough provide reliable, snag-free operation Baffle construction specific for each use: Sewn through for lighter weight (7°C|45°F), Hybrid box baffles in torso/sewn through in leg area (-1°C | 30°F) or full box baffles for maximum warmth (-9°C | 15°F) Zipper length specific for each use: half-length (7°C|45°F and -1°C | 30°F) for ultralight packability; full-length side zip (-9°C | 15°F and -18°C | 0°F) Sea to Summit Guarantee is offered for the Lifetime of this product