Galvin Green Beyla Windstopper Hat – Moonlight Blue Knitted bobble-hat with GORE® WINDSTOPPER® lining. Technology Totally windproof. Effectively protects against windchill. Maximum breathability that allows moisture vapour to evaporate. Thermoregulatory function keeps the body at an optimum performance temperature. Perfect fit for maximum comfort and freedom of movement, specially developed for golfers. Easy to wash and maintain, just regular machine wash. Learn more about Windstopper: The WINDSTOPPER® membrane is an ultra thin, totally windproof protective layer which is laminated to a lightweight textile layer. The membrane is made of the versatile polymer PTFE (polytetrafluorethylene) which is expanded to create a microporous structure. These micropores are 900 times larger than water vapour molecules, allowing perspiration to pass through unhindered.