Founded in 1982, The Sterling Group is a private equity investment firm. It specializes in acquiring and increasing middle-market operating businesses in the fields of manufacturing, industrial services and distribution. Some of its portfolio companies include BTEC Turbines, CST Industries, Hudson Product Holdings, Propex, Roofing Supply Group, North American Energy Partners and Panolam Industries. The Sterling Group has sponsored the buyout of over 30 portfolio companies and several add-on acquisitions for a total transaction value of approximately 8 billion dollars. The firm is located in Houston.