Bag within a bag design. The outer shell is quilted toinsulation. The inner liner is quilted to insulation. When the two layers are assembled, the outer stitching is off-set from the inner stitching. Cold air from the outside cant get through to the inner layer, and warm air on the inside cant escape.

The inner layer of the bag is cut smaller than the outer layer to create a consistent thickness of insulation throughout the bag.This design feature helps prevent thermal leaks from forming, keeping warm air inside and cold air outside.