* The 64K versions (of both Memory Expansion and Silicon Disk) were made only for CPC 464/664. On CPC 6128 they would be useless (replacing the 2nd internal 64K by external 64K).
* The 256K versions (of both Memory Expansion and Silicon Disk) were made in separate versions for 464/664 and 6128 (they should be compatible at software side, possibly the they do differ only cosmetically...?)
* All 64K/256K Memory Expansions, and the 64K Silicon Disc consist of a single cartridge. The 256K Silicon Disc is a special case: It consists of two cartridges shipped together (one contains the ROM, the other contains the RAM).