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-PFC 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-PFC DWR plus a highly water repellent hood and footbox fabric shed wind and condensation. The full-length zipper model can be zipped to an equivalent Women's Spark for comfort that couples can share. DESIGN & DETAILS: RDS-certified, 850+ fillpower goose down with a non-PFC Ultra-Dry Down treatment for maximum thermal performance Ultralight, breathable 10D nylon liner and a 10D shell with PFC-free DWR keeps the hood and footbox highly water resistant YKK #5 zippers with zipper plow provide reliable, snag-free operation Technical hood, anatomical footbox and an ergonomic mummy shape - ultralight doesn't have to mean ultratight Sewn through for lighter weight (7degC|45degF), Hybrid box baffles in torso/sewn through in leg area (-1degC|30degF) or full box baffles for maximum warmth (-9degC|15degF) TECHNOLOGY: Ultra-Dry Down(TM) uses a non-PFC hydrophobic treatment to ensure it absorbs less moisture and dries more quickly QuiltLock(TM) system uses the snap locks located at the shoulder and foot plus the quilt footbox / quilt straps to secure a quilt to the sleeping bag