The GORE-TEX® membrane consists of a microporous structure that contains more than 1,400 million microscopic pores per cm2. These pores are approximately 20,000 times smaller than a droop of water, making it impossible for water to pass through the membrane. BREATHABILITY. On the other hand, the pores of the membrane are 700 times bigger than a molecule of water vapour, which means that sweat can escape to the outside without affecting the waterproofing of the membrane. Preventing heat from accumulating keeps feet dry and warm This makes the boots waterproof from the outside inwards and breathable from the inside the feet to breathe as well as keeping the feet warm.