Engineered to be lightest and warmest synthetic bag available. Proprietary welded Lamina construction enhances loft and eliminates cold spots. Zoned insulation maximizes warmth where it’s needed most. Single 5 half length center zip with dual sliders minimizes weight and still allows for ventilation. Performance mummy cut is snug, reducing girth, weight, and bulk and maximizing thermal efficiency. Comfort footbox follows natural foot position for maximum warmth and comfort. Ultralight shell is soft and highly wind resistant.