The Twin-Tail Boost is an Item Box power-up that appears in the Sonic the Hedgehog series. It is a Boost Item used primarily to increase the user's speed.
Description
The Twin-Tail Boost's icon takes the form of a moving round swirl that is made up of Movie Tails' two twin-tails. In gameplay, this power-up becomes Movie Tails taking flight and moving forward by using his twin-tails like the rotor of a helicopter. While in flight, Movie Tails will be surrounded by an amber aura that leaves a colored trail behind him.
Overview

Movie Tails using the Twin-Tail Boost, from Sonic Forces: Speed Battle.
In gameplay, the Twin-Tail Boost can only be obtained at random from Item Boxes by Movie Tails.
Once obtained, the player can utilize the Twin-Tail Boost by pressing its icon on the bottom of the HUD. When used, the Twin-Tail Boost will increase the speed of the user for a short amount of time. The duration of the Twin-Tail Boost is shown by the decreasing gauge on top of this power-up's icon on the bottom of the HUD whenever the Twin-Tail Boost is in effect. In addition, while the Twin-Tail Boost is in effect, the user will fly high above the lanes on the track, allowing the user to pass over all obstacles and most offensive power-ups without taking damage.
The Twin-Tail Boost can also be upgraded by leveling the user up to level 2, 8 and 14 respectively. For each upgrade, the Twin-Tail Boost will increase the speed of the user while it is active.