Fill power measures the quality and loft of the down used in the puffer jacket. The higher the score, the better the quality and the warmer the jacket will be for its weight.Fill weight measures the actual amount of down in the jacket. A higher weight does not necessarily mean a warmer puffer jacket, as the fill power between two jackets may be different, but it does mean a heavier puffer jacket.It’s best to compare both the fill power and fill weight when buying a puffer jacket to make sure it’s a warmth and weight that works for you.Synthetic and wool insulation use different measures of warmth, so it’s important to read reviews and talk to store staff when making a purchase.Each puffer jacket on this list is a lightweight puffer jacket. Feature photo by Roger Stuart