The fibrous structure is engineered with microscopic pores that readily allow moisture vapor to evaporate but are so small that bulk water and air cannot penetrate.

For the backpacker, Tyvek® provides a waterproof, windproof, breathable, durable, and extremely lightweight material. Tyvek® is puncture, tear, and abrasion resistant. It will not absorb water so it will be lightweight, even when wet - just give it a couple of shakes to get the water off and it's ready to pack.