A borescope is an optical instrument that, in automotive applications, can be used for detailed visual inspection of such components as castings, bent tubes, turbochargers, and engine blocks. A borescope resembles, and functions like, a medical endoscope. It may have a rigid, needle-like inspection tube for looking inside parts such as diesel and gas fuel injector nozzles and bodies, or a flexible, illuminated tube for reaching around corners and seeing into deeper cavities.