CD BackUp RAM Cart
From Sega Retro
The CD BackUp RAM Cart is a memory card that looks like a regular Genesis cartridge, except that there is a blue edging saying "Sega CD", whereas Genesis carts have a red edge. Contains 1024 blocks (1 MBit) of memory for game saves. Some RPGs used this for memory, as there was often not enough space for the save files in the internal backup RAM.