Similar to a Green Shell, the Red Shell will be launched when the Koopa Troopa wearing it is jumped on. In later games, they can also be held and thrown. In Super Mario Bros. 2 (which calls them "Turtle Shells"), they are the only type of shells and are found in grass rather than on Koopa Troopas.
During the events of Super Mario World, Yoshis can spit out fire while in possession of the Red Shell.
In the Mario Kart series, they can home in on the opponent whose rank is one higher than the driver's. Red shells can be picked up in singles or triples, in which case they circle around the kart until all three are fired. In this state, they can be used as a barrier, useful for blocking contact with other hazards, such as Bananas. However, they offer no protection against Blue Shells and Fake Item Boxes. If the character comes in contact with any other driver, then the other driver will be knocked over. The exception to this rule is in Mario Kart: Double Dash!!, where the shells are carried in the hand rather than circle around a character's kart. In Mario Kart DS Wi-Fi mode, a shell could not be dragged by holding the item button.
Red Shells also appeared in the Super Smash Bros. Series. They were in both Super Smash Bros. and Super Smash Bros. Melee. Unlike the Green Shell, which went in a straight path until it fell off, the Red Shell will stay on one platform, and bounce back and forth hitting anyone who hits it (including the user). They disappear over time, however. Notably, the Red Shell is absent from Super Smash Bros. Brawl.
In Mario & Luigi: Partners in Time, the Red Shell is a Bros. Item that is used as a weapon against enemies. When the item is chosen, one of the brothers will kick the Shell towards the foe. It will then bounce off the enemy, cause damage, and come to the other player. After each kick, the shell starts moving faster along the ground. Unlike with the Green Shell, which is only capable of dealing 15 hits, the brothers can then repeat this indefinitely until the player misses a kick. Also unlike the Green Shell, the Red Shell will move on and target another enemy if the chosen enemy is defeated. When the adult and toddler Mario brothers fight together, the babies can sit over the shell and spin upon hitting the enemy, causing extra damage to the foe.
In the Mario Football soccer game series, the item works very similarly to the Green Shells, which are also found in the games, however, they differ slightly in appearance and effect. They are red, and instead of moving in one direction, they home in on the opposing players. Everytime this item is collected, normally is obtained in a group of three. This allows it to home in on three opposing players, however, one will not get hit. These can be used when trying to perform a Super Strike, a Mega Strike, or a Skillshot. There is also a very small chance that the shells might miss the opposing team members, and start bouncing around the stage like a Green Shell. The giant variety of this shell also appeared in the games.
Red Shells reappear in Super Mario Galaxy as an offensive weapon. Like the Green Shells in the game, Mario can only hold the Red Shell, not ride it. If Mario throws the Red Shells near an enemy, it will home in that enemy until it hits something. Underwater, it allows Mario to swim faster and with greater ease. It can also be thrown at underwater creatures and home in on them as well. The other variety of shell that appear in Super Mario Galaxy are Gold Shells, which act like Red Shells when thrown.