The waterproof, breathable material we use is a hydrophilic membrane. It’s a thin but solid, flexible layer which does not allow water droplets to pass through, making it totally waterproof. 

The membrane ‘breathes’ by allowing water molecules to pass. These water molecules are driven through the membrane because of the higher temperature and humidity inside the sock, glove or hat compared to the outside. 

This process is also known as osmosis.