This appears to be an expansion device that attaches to a Nintendo 64 controller and allows you to play Game Boy cartridges. * I recently found a seemingly well-preserved unit at a specialty store (a well-known store where all items are inspected) and bought it out of curiosity, but I don't own an N64 console, so I haven't been able to test its functionality. * I also don't know how to use it or how to play games with it. I hope someone who needs it can use it. ※ Due to its bulk, I will incur approximately 500 yen in shipping costs (Yu-Packet Plus dedicated box + shipping). Please refrain from price negotiations. Hello and welcome, international buyers! I'm just a private seller from Japan who loves vintage items such as retro games. If you are interested in Japanese culture or retro goods, I’d be happy to share them with you. Feel free to use Buyee or other proxy services for bidding. I try to ship quickly and pack items carefully. Thanks for checking out my listing, and I hope you find something you like!