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.