Up to three switches via 3.5 mm TRRS port with optional adapter ^^ Connects to any USB port just like a USB keyboard ^^ Compact - smaller than a pack of chewing gum ^^ Any contact closure can be converted to a USB HID command ^^ Accepts 3.5 mm mono, stereo, or TRRS plugs ^^ X-keys can be programmed with Windows XP-Windows 11 & MacOS 10.14 -MacOS 13. ^^ Linux users should expect to pre-program their X-keys with Hardware Mode prior to bringing their X-keys over to Linux installs ^^ MADE IN THE USA