UFC 137: Penn vs. Diaz (2011)
UFC 137: Penn vs. Diaz was a mixed martial arts event held by the Ultimate Fighting Championship on October 29, 2011 at Mandalay Bay Events Center in Las Vegas, Nevada.
UFC 137: Penn vs. Diaz was a mixed martial arts event held by the Ultimate Fighting Championship on October 29, 2011 at Mandalay Bay Events Center in Las Vegas, Nevada.