SingleCell insulation uses a proprietary technology to weave the insulation directly to the fabric. This minimizes the amount of wind that can get through without adding extra weight. The abrasion-resistant fabric has a DWR treatment that resists light precipitation, and the most vulnerable seams have been sealed to keep water from seeping in. The hood is filled with down, so it wraps your head and neck in toasty warmth while maintaining its ability to pack down remarkably small. Articulated sleeves work with the slim fit to minimize bunching and ensure freedom of motion.