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Mountain Equipment says:
Superb all weather insulation combining warmth, breathability and protection in a single versatile layer.
POLARLOFT Featherless insulation not only works wet or dry but, thanks to it's blown construction, breathes effortlessly as well. Combined with our highly protective DRILITE Loft outer the Superflux is a jacket that thrives as an outer or mid0layer in the most difficult mountain conditions.