Cornerstone Building Brands is the largest manufacturer of exterior building products in North America, serving commercial, residential and repair-and-remodel markets. Headquartered in Cary, North Carolina, it was formed in 2018 through the merger of NCI Building Systems and Ply Gem, and its products include vinyl siding, windows, doors, metal roofing, stone veneer and engineered metal building systems. The company is privately held (owned by Clayton, Dubilier & Rice) and led by CEO Gunner Smith.