• High quality product. 
• Use your PSX joypad, Dualshock, or Dualshock2 on your PC-Engine
• 2 levels of Turbo Fire on A, B, X and Y buttons
• Slow Motion
• Analog function supported : use the analog stick to replace up, down, left and right buttons

It is same as PC Engine Joypad Converter. But the plug is different (bigger).

More info :
PC Engine Classic Joypad Converter