1.6 oz/yd2) is about 2x heaver than the 15D or 10D (0.9 or 0.67 oz/yd2) fabric on many of the quits. Since the shell material is a major weight contributor of sleeping bag or quilt this really matters. And of course there is no material under you or on a hood in a quilt which also saves weight. 800 to 800 fill power down vs. the 700 fill power on the Zissou. E.g. your down is about 20% heavier for the same warmth. That is 15,000 in3 of down weighs 21.4 oz for your bag and only 17.6 oz for 850 fill power down quilt (and in the quilt more of that down is over your body because there is no down under your body so it’s even wamer). Less weight for draft tubes, zippers, drawcords and toggles etc. There are more of them and heavier versions in your bag. Yes, these do add up.