You will often see files ending in .nsp or .xci . Here is the difference and why you might be looking for an NSP:
Buy a used physical cartridge for $40. Buy the DLC pass. You own the cartridge, but the update to 303 lives on your SD card.
Race as your favorite Nintendo icons across 48 base tracks, plus dozens more available via the Booster Course Pass [3, 4]. Gravity-Defying Mechanics: