The Memory Expansion Pak, much like the Rumble Pak, is a DS Option Pak accessory for the Nintendo DS and DS Lite. It is inserted into Slot-2, and it adds 8 MB of RAM to the system, as well as a memory management unit, for a total of 12 MB. The accessory is available in two versions: one for the original Nintendo DS, and one that exclusively works with the DS Lite. (The original version is also compatible with the DS Lite, although the cartridge protrudes from the console.) Retailers carried both versions in Japan and Europe, but other regions only sold the DS Lite version at retail, while Nintendo made the original version available by mail order.