This adapter works fine for the Super Smash Bros game on Wii U, and it will also be the only game that you can use, which is a shame nonetheless. It is a pleasure to play this game with my GameCube controllers!
The quality is good, although 20 4 just plug controllers, it is not given.
Moreover, it would have been preferable Nintendo happen in numbers, to prevent speculators seized product for resale up to 4 times its original price.