A baselayer top is the foundation of any outdoor layering system. Choosing a breathable t-shirt will help to manage perspiration better, keep your body cool and ensure you stay comfortable while active.
Combine your breathable baselayer with an insulating midlayer such as a fleece jacket or down gilet during colder months to ensure that you keep vital body warmth where it needs to be. The idea behind the outdoor layering system is that it is always easier to layer up or remove layers to manage your body heat than it is to cool down or warm up by simply using thicker or thinner items of clothing. Baselayer tops can be combined with a pair of baselayer leggings to create extra insulation under your clothes for additional warmth.