Wearing the correct base layers is one of the most important things to do when you are motorcycling. Too often customers spend a lot of money on a decent suit and then ruin it by wearing a cotton T-shirt! Base layers need to be a proper breathable material so they help you regulate your body temperature.  It is about keeping warm in winter, keeping cool in summer, allowing your body sweat to evaporate effectively and allowing your expensive suit to do its job properly. Even in winter sweat needs to escape to keep the body dry. And this is crucial because if you are wet on the inside, and the temperature drops further our bodies will lose heat 20 times faster through a wet environment than a dry one. The base layer is a building block in winter on top of which you need a technical mid layer.