This is a cartridge for the ZX Interface 2.021, a new cartridge interface for the ZX Spectrum 16k/48k machines that includes a Sinclair joystick interface - just like the original. The cartridge slot have been expanded in order to expand the maximum cartridge size beyond the initial 16k using bank switching, mainly allowing me to create cartridges with just a handful of components. This specific allows you to use ROM chips varying in size from 27C128 to 27C512, allowing you a combined size of 128K ROM space - that's enough to hold around 80% of all of the originally released cartridges.

There is a dedicated faceplate for this cartridge, but more will probably be added at a later date..