Fit and compatibility
This key fits SIMATIC S7-300 and S7-400 CPUs that accept the standard Siemens key for the mode-selector switch. It is not a functional substitute for a CPU or any electronic module — it is purely a mechanical spare. If your panel was specified around a 6ES7518-4TP00-0AB0 CPU, that unit uses a different key design; the 6ES7911-0AA00-0AA0 will not physically interchange without verifying the CPU front-panel keyway.