A word about Extira from the manufacturer. "An exhaustive research and evaluation of alternative substrate materials eventually lead us to a material that met our exacting parameters in terms of performance, durability and final appearance. The patented TEC™ technology utilized in the production of Extira met those criteria and then some. A unique and proprietary steam injection, sealed-press process provides the weatherability, uniform density and machinability we sought. Phenolic bonding delivers the durability and moisture resistance factors and zinc borate treatment assures maximum rot and termite resistance."