It resembles a charcoal Commodore 1541 and plugs into the cartridge port for faster access than the C64 / 1541 combo. Commodore reportedly planned an interface to allow use of the 1551 with the C64, but it was never released.

Aside from faster access, the disk is very similar to the 1541. Like the 1541, it is a single-sided 170 kilobyte disk for 5¼ "disks, with each disk split into 664 256-byte blocks available for user data plus 19 blocks for DOS. data and directory; the file system makes each block its own cluster.