Inlet cones (sometimes called shock cones) are a component of some supersonic aircraft. They are primarily used on ramjets, such as the turboramjets of the SR-71 or the pure ramjets of the D-21 Tagboard and Lockheed X-7. More examples of inlet cones can be found on the Su-7 Fitter and the MiG-21 Fishbed, both of which use conventional jet engines.