Pertex Quantum fabric is layered on top to shield wind and improve its efficiency. WarmCube construction with 80g PrimaLoft Silver Hi-Loft and 120g Recycled Thinsulate Featherless. 3M Thinsulate Featherless insulation is as warm as 700-fill-power down and stays warm even when wet; PrimaLoft Silver Hi-Loft insulation provides breathable, lightweight warmth.