I have one adaptor too. It can switch into 4 different types of inputs (2,4 axis, 4, 4 axis etc)
It came bundled with an 8-way small arcade stick. I was surprised to find that for fighters (emulated and DirectX) this is faster and more responsive than the Hori V3-SA, which uses a square gate. I have to convert that too but it works with a little effort. too bad that for buttons I have to use the keyboard instead.
It works with simple joysticks like the Gravis Gamepad but unfortunately if I plug the serial version of Microsoft Sidewinder Gamepad (my favourite), it does not register correctly and not all buttons are recognized.