One of the most important characteristics of a well defined sleep system is the differential cut.

A differential cut is when the outer shell of a quilt is cut wider than the inner shell to fully allow the down to loft and reduce compression when pushing up against the inner.

This not only allows for greater efficiency of warmth, but it also give the quilt a better 'wrapping' ability in which it will stay underneath you more easily as the quilt is shaped by the differential cut.

I currently only offer these on my sleeping bags