It may be just as light and lofty, but high-tech PrimaLoft insulation does down one better: It holds its warmth even in wet conditions. Witness its power when you battle the elements in a core-warming nylon vest that offers the equivalent of 600-fill-power down. Wear it as a core-protective layer on the coldest days, or pack it along for lightweight but serious emergency protection on backcountry runs. Style Name:The North Face 'Thermoball' Packable Primaloft Vest. Style Number: 430134. Available in stores.