A fire jet[1] (also called flame spurt[2]) is a mechanical flamethrower found in Super Mario 64 and its remake.
Fire jets are indestructible diamond-shaped objects with a hole in the center. They appear in all of Bowser's levels, as well as other courses like Lethal Lava Land and Rainbow Ride. About every three seconds, a fire jet shoots a stream of fire from its center. If hit by the flames, the character will lose three life points and will start to run around, making it difficult for the player to control them. If the player's character jumps around while they're on fire, their movement will be limited and may only take two points of damage.