30+ Years of American Manufacturing Born innovators, Cornerstone Valve led early commercialization of custom engineered valves for severe service applications. Today, we are recognized as a leading manufacturer of custom engineered ball valves for severe service applications. All of our products are designed, manufactured, assembled and tested under one roof in Houston, Tx we’ve called home since our founding in 1990. Not only are our products are designed and produced here, majority of our suppliers are based in the USA, too – most right here in Texas. With such a tight-knit domestic supply chain, the typical turnaround time on our made-to-order product is fastest in the industry. We are available 24x7 for after market support. We operate on ISO 9001 quality management system standards – a certification we’ve maintained since 1997 – so you can be sure any product you purchase is quality-built by Americans who are proud to uphold the tradition of excellence.