The Nike ACG Lava Flow Therma-FIT ADV Vest is an insulated vest that pairs PrimaLoft fill with Nike's Therma-FIT ADV tech to regulate heat and hold warmth in cold conditions. A water-repellent nylon shell covers the insulation, so damp air has a harder time cutting into that warmth. What Our Gearhead(R) Experts Are Saying:"I clip it to my pack all day on camping trips, then pull it on the minute the evening turns cold. The sleeveless build keeps my core warm while my arms stay free for cooking and pitching the tent. By morning it folds into its own pocket and clips back onto my pack for the walk out."