From the Super Mario Wiki
Retrieved from "http://www.mariowiki.com/index.php?title=Black_Shell&oldid=2077917"
Black Shells are usable items that appear in Mario Kart Arcade GP, Mario Kart Arcade GP 2, and Mario Kart Arcade GP DX. Its effects are similar to that of a Winged Spiny Shell, though unlike a Winged Spiny Shell, it can only be fired straight and has a higher appearance rate. They explode upon impact of a wall, obstacle, or other racer, sending those caught in the blast soaring for a second. They can also be used as a triple if unlocked.