This new version of the pro aero ls jersey with updated fit and fabrics packs lightweight wind protection with superior ventilation and is perfectly matched with pearl izumi39s transfer wool ls baselayer added insulation on the chilly autumn days windproof chest and arm panels cut the breeze while summer weight jersey panels in the underarms and back let you dump unwanted heat an excellent do it all layer for transitional seasons best paired with pro thermal bib tight or pro thermal bib