Secondary Offering for Mistras Group Shares

Washington, D.C., May 2011

Thayer | Hidden Creek is pleased to announce that TC NDT Holdings, L.L.C., an affiliate of Thayer | Hidden Creek, has sold all of its shares of stock in Mistras Group, Inc. (NYSE: “MG”). The 2,764,401 shares were sold in a Public Secondary Offering which closed on May 11, 2011 at a price of $16.00 per share.

Mistras is a leading global provider of technology-enabled asset protection solutions used to evaluate the structural integrity of critical energy, industrial, and public infrastructure. Mistras combines its industry-leading products and technologies, expertise in mechanical integrity (“MI”) and non-destructive testing (“NDT”) services and proprietary data analysis software to deliver its customized solutions. These solutions enhance the Company’s customers’ ability to extend the useful life of their assets, increase productivity, minimize repair costs, comply with governmental safety and environmental regulation, manage risk and avoid catastrophic disasters.