A simple example of ejector nozzle is the fixed geometry cylindrical shroud surrounding the afterburning nozzle on the J85 installation in the T-38 Talon.[11] More complex were the arrangements used for the J58(SR-71) and TF-30(F-111) installations. They both used tertiary blow-in doors (open at lower speeds) and free-floating overlapping flaps for a final nozzle. Both the blow-in doors and the final nozzle flaps are positioned by a balance of internal pressure from the engine exhaust and external pressure from the aircraft flowfield.