The Commodore 1541-II is the second of two upgraded versions of the CBM 1541 (the first upgrade was the 1541C) disk drive. The 1541-II has the more modern 'radial handle' locking mechanism.
This disk drive connects to the Commodore 64 (or 128) and is a single-sided 170 kilobyte drive for 5¼" disks.
The disk drive uses Group Code Recording (GCR) and contains a MOS 6502 microprocessor, doubling as a disk controller and on-board disk operating system processor. The number of sectors per track varied from 17 to 21 (an early implementation of Zone Bit Recording). The drive's built-in disk operating system is CBM DOS 2.6.
Use of "flippy disks", which were double-sided disks converted by cutting/punching a notch on the left-hand side, would give access to the reverse side of the disks and effectively double the storage capacity. The notch could be made with a knife, single hole paper punch, or "disk notcher" tool that was specifically designed for this task.