Filson Ultralight Jacket. With an exceptional warmth-to-weight ratio, the Filson Ultralight jacket can be worn as an outer layer, or midlayer under a shell. Made with ultralight PrimaLoft® Gold 60-gram insulation that retains warmth even when wet, and a durable, 1.5-oz. ripstop shell. Features an interior zippered pocket and moleskin-lined handwarmer pockets.