TPU fabricĀ is created by laminating the membrane to high-performance textiles that are extremely breathable, then sealing them with an innovative solution for 100% waterproof protection. The TPU membrane contains microscopic pores, which are a 1000 times smaller than a drop of water, but 100 times bigger than a molecule of moisture vapour. So whilst water droplets cannot penetrate the TPU membrane, moisture vapour can easily escape.