DESCRIPTION: This graphic creates some impression of just how substantial the newly renovated exterior wall of the Pentagon was. There was also a layer of Kevlar mesh, the same material bullet-proof vests are made of. The building performance report says, "The perimeter exterior walls of Ring E are faced in limestone and backed with unreinforced brick infilled in the concrete frame. Nearly all remaining exterior walls are 10 in. concrete. The first-story at AE Drive is brick infilled in the concrete frame, with no windows." The following photo shows the exterior wall. The rebar in the concrete is what is meant by "reinforced".