Made in Japan. Allows you to use mark 1 cartridges (the Yamaha DX7 ones basically) in mark 2 slots (Yamaha DX7II-FD, DX7II-D, RX5, TX802, and so on). While voice data from the first generation of 6op synthesizers is compatible with the second generation, it doesn't work the other way around, hence the need for a different size and connector layout of the new cartridges (that also include new features).