Breathable jackets will allow perspiration to escape, without becoming damp and cold. The higher the breathability the better moisture will be transported to the outside. The level of breathability is recorded in grams of water vapour per square meter (g/m2) and it is measured over 24 hours. A higher level of breathability will mean a higher “g” rate. A standard fabric might rate at 5,000g whereas a higher end product could reach up to 20,000g. Watch the video for more information.