Filson Ultra-Light Vest. Filson's Ultra-Light Vest is the perfect outer layer during mild days and the ideal midlayer on cold winter days. Ultralight PrimaLoft Gold 60g insulation has an exceptional warmth-to-weight ratio, and retains 98% of its insulating properties when wet. The abrasion-resistant Cordura ripstop nylon shell has an elasticized waist to keep a low profile for easy layering under a jacket. Soft, comfortable Moleskin-lined handwarmer pockets and collar facing.