The Triple Red Shell, first introduced in Mario Kart 64, affects the player in the same way as a Red Shell, however, there is three of them and they also rotate around the kart. In Mario Kart: Double Dash!! Triple Red Shells (and Triple Green Shells) are the Special Item of Koopa Troopa and Paratroopa. Petey Piranha and King Boo can use three Shells, too.
Triple Red Shells, once released, will home in on an opponent ahead of you and hit them. They can also be dragged behind you.
The only exception to this rule is in Mario Kart: Double Dash!!, where the shells are carried rather than circled around a character's kart, either by juggling them or in a stack. Getting struck by another item will disrupt the character holding the shells, dropping all but one. In Mario Kart: Super Circuit, Red Shells have an additional function. It can also be planted behind the racer instead of released forward. The shell will not rocket forward, but sit on the track, slowly rotating around. If another driver comes within range, the Red Shell will squeal three times and immediately smash into the racer- even if said racer was the one who set the shell on the track. This is useful for competitors sitting in first place, who have no one to target but the drivers trailing behind them. If a player is in first place, Red Shells do not target anyone; depending on the game, they either travel in a straight line or follow the track, until hit an item or obstacle.