Helly Hansen Prowool Stripe Crew Base Layer

In order to be comfortable, your skin needs to stay dry. LIFA base layers help this happen: they are made from polypropylene, which pushes moisture away from the body to keep it dry and warm.
Polypropylene is a hydrophobic fibre. This means that polypropylene - unlike cotton or wool - does not absorb moisture so the fabric stays dry next to your skin. In addition, tests have proven polypropylene to be much more efficient than other synthetic fibres, such as polyester, at transporting moisture. The result? You stay drier.
It works on the theory of body heat transfer. LIFA uses body heat to push moisture along its fibres to the outside of the garment, where the moisture quickly evaporates or is taken up by the second layer.
Polypropylene has other qualities that make it an excellent choice for base layer clothing. It is soft on the skin and lightweight to wear. It is non-allergenic and a good insulator. It also retains its shape, which allows the best fit for each individual. A close-to-body fit, combined with excellent elasticity, prevents any moisture being trapped between skin and LIFA, and allows free passage of perspiration and heat.
More good news - LIFA is permanently resistant to bacteria so, even after prolonged use, it does not retain odour. This is because LIFA is made of endless multi-filaments of polypropylene twisted together to form a single-filament yarn. Without fibre ends, there is nowhere for odour-generating bugs to bed in, and no opportunity for the fabric to pill.
Wool has excellent insulation properties, polypropylene absorbs less moisture than any other fibre. Blending them together creates the perfect base layer for low-energy use in cold climates, for example, Ice Climbing.