Tee rate depends of your preference, If you  want only play nds games in my opinion  must to be higher like 90% or 92. I have this flash carf and I prooved a lot of games and almost all ware working with any problem.

If you want play homebrew and nds games mmmmm..  some homebrew Its actually working but others no. I tried to play with SNEmulDS  and always is frezeer when I must to put  start and Y have to reset my console. In this case the rate have to be around 75%.

If you want to play another gba games betters buy another flashcard o ewin2pro  (this version can play gba games.)