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Mountain Equipment says:
A hybrid vest with an insulated front and low profile grid fleece back for fast moving mountain sports. Highly breathable and fast drying POLARTEC® Alpha® insulation is combined with our lightweight 20D RS shell fabric in the front of the body for wind resistance. Pontetorto® Tecnostretch 187 panels in the back and sides minimise bulk and dry even faster after a strenuous ascent.