Form-fitting synthetic or natural base layers are a great piece of clothing to wear in cooler to temperate conditions where you will be exerting a lot of energy.
The garments trap air between their fibres keeping you warm at the start of your activity. Then when you start to work and sweat, the base layers wick away this excess moisture cooling your skin and keeping you dry and comfortable at the same time. These base layers are an essential piece of kit that everyone should own who enjoy outdoor sports and activities; especially at a discounted price.