Velocity 6

Velocity 6 ["Legends of Today" / Flash Season 2]
Velocity 6 was a drug to increase a speedsters speed and power gained through the speed force for a limited time, and in the case of Jay Garrick and those who previously were speedsters, renew temporary access to their previously lost powers. Conceived by Harrison Wells of Earth 2 but all his attempts were unsuccessful until "Legends of Today" where Caitlin Snow used her biochemistry background to get a working serum. Jay Garrick provided a word of warning to Caitlin about using this "drug" to increase a given gift and that it is not to be used, however when in a dire situation Jay injected himself to phase through Wells [Earth 2] to retrieve a bullet and save his life.

Easter Egg [Comic Relation]
A similar drug/serum was created by Vandal Savage in the comics with the ability to give a temporary speed enhancement and was called Velocity 9 and was sold in the drug trade.

The use of Velocity 6, a drug with similar effects to Vandal Savage's comic book Velocity 9 is a cool easter egg to the villain who also made is first appearance in "Legends of Today" alongside Dr Wells [Earth Two] creation of a working Velocity 6 Serum. Vandal Savage set his role as the main villain in the upcoming tv show "Legends of Tomorrow"