The CleanSpace 20 mil vapor barrier is a 7 ply, string reinforced, polyethylene liner with a built-in antimicrobial. As a result of its thickness it will stand the test of time against a normal crawl space wear and tear. It is durable enough for home owners to use their crawl space for storage without worry of tearing the liner and is sturdy enough for servicemen to crawl on it without puncturing or tearing the liner. The CleanSpace 20 mil vapor barrier is also backed by a 25-year transferable warranty.