Level-boost ticket

Level-boost tickets are items in Mario Kart Tour used to increase the skill level of a specific driver, kart, or glider by filling up the gauge to level up with 1. If the driver, kart, or glider has already the maximum skill level, no further level-boost tickets can be used. Silver level-boost tickets can be obtained from Tour Gifts. Golden and amethyst-golden level-boost tickets can be obtained from Tour Gifts as well, but only if a player is subscripted to the Gold Pass.

In-game description
"Raise a Normal/Super/High-End driver's/kart's/glider's skill level."