It resembles a charcoal-colored Commodore 1541 and plugs into the cartridge port, providing faster access than the C64/1541 combination.

The DOS limits the number of files per disk to 144 regardless of the number of free blocks on the disk because the directory is of a fixed size, and the file system does not allow for subdirectories.

Its DOS is compatible with the 1541, so disks written by one drive can be utilized in the other.

The 1551 has no DIP switches to change the drive's device number.

If a user added more than one drive to a system, they had to open the case and cut a trace in the circuit board to permanently change the drive's number, or hand-wire an external switch to allow it to be changed externally.