F-Zero X Expansion Kit (エフゼロ エックスエクスパンションキット,Efu-zero Ekkusu Ekkusuekusupanshon Kitto?) was an expansion to the original F-Zero X that was released exclusively on the Nintendo 64 through the Nintendo 64DD add-on. It was the first of a few expansion packs that were released on the service, with one for Doshin the Giant being released a month later. The game offered fans of F-Zero X new features such as a vehicle and track creator, as well as 12 new tracks made exclusively for the expansion kit. Other changes or additions were made as well, and all of the features, tracks and vehicles of the previous game could be accessed once again.
Twelve new tracks that were separated by two cups were included.
A create your own track was included. You could save up to 100 of your own custom made tracks. The track creation tool is so unique as it was the same tool that the designers used to create the game's tracks.
You can save three ghost racers per course.
The game includes a Car Editor that lets you create your own vehicle using pre-made parts.