PS/2 & USB Trackball Interface Kit - 2-1/4" & 3" Trackballs: Kit converts existing 2-1/4" or 3" Suzo-Happ trackballs to work with USB or PS/2. Simply replace the optic boards on the existing trackball with the included new optic boards and harness. Connects directly to either a USB or PS/2 port on a PC. Compatible with Windows 98, Windows 2000, Windows ME, and Apple Macintosh iMac, Power PC, with OS 8.5 or higher, Linux with USB HID support. No external power supply needed. Automatically detects whether it is connected to a USB or PS/2 port and configures itself accordingly. Supports up to three buttons (sold separately). Includes both .187" and .250" terminal connectors for pushbutton switches. For 4-1/2" Suzo-Happ trackballs use 56-0114-00K.