Lot of two 1980s Casio ROM Packs RO-255 (Rock On) and  1 @ RO-551 (World Songs) are  electronic keyboard accessories designed for use with Casio keyboards. Made in Japan, these ROM packs adds a collection of World and Rock songs to the instrument's repertoire, allowing users to play a variety of musical styles from around the globe. Compatible with typical models from Casio’s PT, MT, CT, SK and DH series that support ROM Packs.  Verify that these will work on your device.