The Siemens 6ES7953-8LG11-0AA0 is a SIMATIC S7 micro memory card — 128 KB capacity, 3.3 V NFlash — designated as a spare part for S7-300, C7, and ET 200S IM151 CPUs. This is the card that holds the user program and configuration data for those controllers; if the original card fails or needs replacement for a backup CPU, this is the direct Siemens order code to source.
What Fits Where
This micro memory card plugs into the slot on S7-300 CPUs (including the 31xC and 31x series), C7 compact units, and ET 200S IM151 interface modules. The 3.3 V NFlash interface is specific to Siemens S7-family CPUs — it is not a standard SD or MMC card. No special tooling needed; the card clicks into the CPU front slot and the controller reads it on power-up. If you are swapping a failed card, power down the CPU, insert the new card, and power back up — the CPU loads the program from the card automatically.