Pertex Endurance technology incorporates an ultra-thin membrane with a durable nylon face fabric. This layer is so thin that it hardly adds any weight, nor does it affect the softness of the material considerably.
One thing we learned from sleeping outside is that your bag tends to get wet. Pertex Endurance fabrics have one main objective to provide maximum protection from moisture. This works both ways: Keeps water, snow and wind out, allows moisture to pass freely from the inside this keeps your bag dry from condensation.
Pertex Endurance technology incorporates an ultra thin, air permeable membrane that is both highly breathable and water and wind resistant. This layer protects the insulation material from the elements to maintain loft and retain warmth.