Natural down still has the best insulation and compression properties. Synthetic fibre imitation of down copies its structure and profile. It is also called 3D fibre. It is a consistent thermal insulation layer that protects against body heat loss. Advantages include simple maintenance, fibre coherence, and shape memory. And the greatest benefit is that it retains insulating properties even in humid environments. This makes it a popular choice especially for cold and humid weather activities, such as skiing and alpine skiing.