Harkila Driven Hunt Insulated WaistcoatHarkila Driven Hunt Insulated Waistcoat The lightest and most efficient natural and man made insulating downs combine to provide a superior level of thermal warmth in this winter gilet. An innovative thermal system sees the front lined with certified, traceable duck down* the lightest and most effective insulation material available for clothing, whilst the back and sides are lined with high loft, 120 gram, Thermo Poly Shield Down Feel wadding.