Velocity 9 is an item that can be taken by any player (regardless of whether they are a Speedster or not), that will give them a temporary speed boost and gives speed sickness once finished
The potion will affect the player for ten minutes, and the speed is not changeable (though if you are a speedster, you can toggle the speed force on/off).
For numerical values, the potion will give 3 extra Speed Bars.