Box Stitched Down Comforter construction is produced by taking (2) large sheets of fabric (sewn around the outside perimeter) then the compartment is filled with Down.
Once filled, this compartment is then sewn/quilted in a defined pattern (generally a square). This construction keeps the Down from shifting, which provides even warmth.
Although this construction is preferred over those that don’t have sewn containment chambers, sewn through Box Stitch Comforters do not allow the Down to loft to its fullest capability and are generally a lower cost product than a Baffle Box style of Comforters.