Site 2Page 3Page 4Page 5Page 6Page 7Page 8Page 9Page 10Page 11Page 12Page 13Page 14Page 15Page 16Page 17Page 18Page 19Page 20Page 21Warmth. Insulation matters, but the amount of of it depends on the typical winter temperatures you are in. Down jackets will usually specify its "fill electric power," or simply how much down is inside; jackets with a