When I first bought my N64 the expansion came with it. I didn't know much about expansion packs until I searched online. It basically improves the resolution and graphics in the games you play. I know that it only works for some older games like mario kart 64, or super mario 64. Required games are donkey kong 64 and the legend of zelda majora's mask. It's pretty good I guess accept I kinda wish it worked for all games.