Lighten up so youll be the one singing the last mile into camp. The Spark doesnt compromise comfort or warmth to shave ounces. We use partial Flex construction to keep the luxury meter pegged without adding noticeable weight. Youll sleep more comfortably, and more warmly, than ever before with Flex. Just to prove were still attached to the details, we include all the bells and whistles, like Foot Box Venting, to make our Ultralight Spark as comfortable as bags weighing twice as much.