Incorporating their 2D PermaShell fabric and a premium 650 loft down, Sea to Summit Trek bags are a refined classic. The 6040 fill ratio in the Trek bags is maintained using a side block baffle and differential cut shell. In the top of the shell a 3D side wall, a feature normally reserved for technical alpine sleeping bags, provides more space for the down to loft right to the edge of the bag.An oversized security pocket located inside the bag is easily accessible, ideal for stashing passports and other valuables while travelling. The soft touch lining fabric is down proof by construction and highly breathable offering a comfortable sleep.The tapered rectangular design offers a good compromise between the comfort of a generous cut shape and warmth of a closer fit. A full length side and foot zip allow the Trek series to be opened out into a full duvet for use indoors and warm weather.