The Memo5+ is a Memo5 cartridge with 512K of ROM. There is no banking support, instead a ROM can be selected with a dipswitch. The Memo5+ is compatible with all MO5 and MO6, even the first generation ones (which lack some wiring on the Memo5 port).
There is no banking support, so only 16K cartridges images can be used with it. The goal is to run Macro Assembler.