Contour Design ShuttlePRO V.2 9 of the programmable buttons have removable keycaps for easy labeling Inner Ring (jog) - rotates through 360 degrees and provides frame by frame control Outer Ring (shuttle) - rubberized and spring-loaded for fast forward & rewind functions Jog & Shuttle can also be used for scrolling, volume control, sequencing & more! Macintosh Requirements - PowerBook, iBook, iMac, G3, G4, or G5 running Mac OS 8.6 through 9.x or OS 10.1 or later, available USB port, and 10MB of free hard disk space