The 1764 Ram Expansion Unit plugs into the cartridge port of a Commodore 64 and provides an additional 256 KB of RAM. Though not designed for the Commodore 128, it is reportedly compatible with it. It also came bundled with a replacement power supply for the C64, as the C64's stock PSU could not provide enough current for both units.

The 1700 and 1750 are similar to the 1764, but are designed for the Commodore 128 and provide an additional 128 KB and 512 KB of RAM respectively. Though not officially compatible with the C64, they can work on the C64 as long as a different PSU is used.