Fill shift can cause a cold spot running from the neck to the waist on conventional design sleeping bags.

The One Planet Vertical Cross Baffle System was engineered to prevent this fill from shifting, creating a warmer bag with absolutely no increase in weight.

The Alpine Series bags use the Vertical Cross Baffle System so that you stay warm all night long. The chest baffles in these Mummy shaped bags run vertically and those from the waist to the foot run horizontally, countering fill movement caused by a body in a bag. All baffles are sewn off so the fill can't move.