If you are working on a very new PC (2023 or newer), I'd recommend grabbing the latest available version rather than specifically v21.12 to ensure your hardware is recognized correctly.
Version 21.12 is one of the final major releases of the "classic" Medicat lineup before the project shifted focus. It is prized for its stability and the breadth of tools included. Medicat Usb V21.12 Iso Download