The Nintendo 3DS Game Card is a small cartrige like item that holdes a game's info. It is placed in the 3DS game Card slot. Unlike the DS, 3DS Game Cards have a small tab on the top of the right side, which prevents it from being put into older systems.
The Game Card is light gray, and is roughly square-shaped, with slightly more of a curve on the bottom-left corner. The cartridge is also the same size as a Nintendo DS game card, except for a small tab on the side which is meant to prevent it from being inserted into an older DS system. There is also a sticker on the front with the game's title on it. On the back, the contacts can be seen, and there is a model number printed onto the card.