This is a small PCB which will plug into the side of your TI-99/4a joystick port and then make use of any Atari 2600 compatible Joystick! It has two ports to allow both players to use their favorite controller.
The original TI joysticks are hard to find in good condition. There is only one port for both controllers which makes third party controllers rare. This left you with few options, but now, you can use your a wide variety of controllers on your TI!