Gathered Quilt™ System - All Alpine Down Huggers use MontBell's patented Gathered Quilt™System. This system is similar to our Super Stretch™System, and consists of elastic sewn into the baffles on the inside of the bag. This system allows the shell of the bag to keep its full shape while drawing the interior closer to the user, creating a much more efficient bag. The elastic baffles also allow the bag to stretch as the user moves and changes position. Thus, the Gathered Quilt™System provides the freedom of movement of a more generously cut sleeping bag while providing the efficiency of a much closer fitting, more restrictive bag. Because of this increased efficiency, MontBell is able to use less down to achieve the same warmth, making the bags much lighter per warmth than other sleeping bags.