HeliumAP is a subset of our Helium fabrics program, where ‘AP’ denotes air permeability. HeliumAP has been exclusively developed by Mountain Equipment in conjunction with our fabric mills. Fabrics which are air permeable offer significant advantages in active insulation because of their improved breathability. However, they tend to suffer from decreased strength as the yarns used to make them have to be woven less tightly than regular shell fabrics. To ensure the perfect blend of air permeability and strength we have woven our fabrics with different weave densities in the warp and weft directions, ensuring that air can pass through the fabric, but without the fabric’s mechanical performance being affected. This means you maintain strength, improve breathability, and have the soft handle of a premium shell fabric.