Eco GameCube Adaptor (with 5pcs double-faced tape)

The adapters themselves, are of course necessary.

But these stickers are complete garbage. They stick too strongly during the first 1-2 uses (you have to remove the disc very carefully), and after 3-4 uses they don't stick at all anymore. That makes the four replacement stickers pretty pointless.

You're basically forced to come up with your own solution, for example by using Fixogum or very thin removable double-sided adhesive dots to prevent the disc from rotating inside the adapter and causing circular scratches. You'll have to experiment a bit to find what works best for you.