John Petrucci tests Ernie Ball Cobalt strings

Ernie Ball's strings and accessories are available in more than 6,000 music stores throughout the U.S.
Lot of Ernie Ball's products are presented by highly acclaimed musicians, just like John Petrucci in this video.
Petrucci, best known as a founding member of the progressive metal band Dream Theater, is presenting new Ernie Ball Cobalt electric guitar strings