Digital ferrule scopes are commonly used in production and by field installers to inspect ferrule surface quality and comply with this specification. The type of inspection needed depends heavily on the application, the ferrule material, and the code or standard governing the connection. Visual Inspection. This video showcases our self-developed concentricity testing equipment for ceramic ferrules. Tools • 1 - 1/4” Open End Wrench • 1 - 3/8” Open End Wrench • 2 - 7/16” Open End. Ceramic ferrules are short, cylindrical or sleeve-shaped components made from refractory ceramic material — typically high-alumina or mullite-based compositions.