At Thermo-Twin, we take pride in the quality and craftsmanship of every window that crosses the assembly line. Product quality begins with quality materials. Each of our multi-chambered extrusions are manufactured from 100% virgin vinyl (NEVER recycled), permitting low maintenance and providing outstanding strength and rigidity. Welded frame and sash corners provide extra strength for lasting durability and smooth operation. To protect your home comfortable and safe from the elements, our windows come standard with weather stripping to guard against air infiltration, providing increased energy efficiency.