The Siemens 6ES7953-8LF11-0AA0 is a SIMATIC S7 Micro Memory Card designed for S7-300, C7, and ET 200S IM151 CPUs. It stores user programs and data on 64 KB of 3.3 V NFlash memory.
The card plugs directly into the MMC slot on the CPU module. It operates at 3.3 V logic, so verify CPU compatibility if migrating from older 5 V CFast or EPROM-based systems. The 64 KB capacity suits smaller logic blocks and parameter sets for distributed I/O stations.