The 128K RAM Solid State Disk (SSD) fit inside the Acorn Pocket Book and provide additional space for storing information. They are smaller and more robust than floppy or hard disks because they have no rotating parts. Information can also be protected from accidental deletion by moving a write-protect switch.

Acorn produced two different types of SSD. RAM discs which are normal read/write discs with a backup battery to protect the contents when the SSD is removed from the Pocket Book, and Flash discs which are write-once discs which preserved their data. The Flash SSD can be reformatted, but all data is lost. The RAM SSD is best for storing information that is frequently altered, such as the personal files that you are currently working on. Flash SSDs do not require a back-up battery to retain data, and you can read and write to them, but deleted files still use up space (which can be recovered by reformatting the disc). However, Flash SSDs are more cost-effective than the RAM SSD and are ideal for material you wish to access frequently but seldom change, such as software programs, resources and personal files you wish to archive.