Exhaust nut with hex socket. Used for securing heat exchangers on 911 models and for other uses on other models.

To fit:
911 1965-1989 6 required per engine for heat exchangers
930 1975-1989 6 required per engine for heat exchangers
914/6 1970-1976 9 required per engine for heat exchangers
924 Turbo/GT 1979-1984 2 required for securing turbocharger to mounting
944 S 1985-1988 2 required for securing air flow meter to mounting
911 (964) 1989-1994 2 required for securing power steering pump
911 (964) 1989-1994 4 required per engine for heat exchangers
911 (993) 1994-1998 5 required per engine for heat exchangers
911 (993) Turbo 1994-1998 4 required per engine for heat exchangers