SLAYER guitarist Kerry King tells Classic Rock magazine that he doubts there will be any more shows featuring the so-called "Big Four" of 1980s thrash metal — METALLICA, SLAYER, MEGADETH and ANTHRAX.

"If you look at how much work went into making it all happen in the first place, then I really doubt we can do the same thing again," King says. "You had four headlining bands touring together and that takes so much organizing."

He adds, "I know there are some parts where they're angry not to have gotten the chance to see it. The Bay Area will probably never forgive us. And we could go on and on doing it for ages. But I honestly doubt we can get our schedules to coincide like that again."

The "Big Four" played the seventh concert of this year's tour on September 14 at Yankee Stadium in New York City (The bands played together a number of times last year in Europe as the "Big Four" and at large festivals.)

The idea for the "Big Four" tour first came up in 2009 and METALLICA drummer Lars Ulrich told The Pulse Of Radio he was glad to finally see it happen. "It's pretty amazing, if you think about it, that it's the first time basically in 25 years or 30 or whatever that the four of us have actually played shows together," he said. "So it was a lot of fun, a lot of memories, a lot of fun times — new fun times, and fun times talking about the old fun times. So it sort of was a, it was a winner on every front."

This past spring, METALLICA, SLAYER, MEGADETH and ANTHRAX were presented with double-platinum plaques for the two-disc DVD release of "The Big Four: Live From Sofia, Bulgaria", containing footage of the June 22, 2010 Sonisphere cinecast from the Sofia, Bulgaria leg of the touring rock festival featuring all four groups. The presentation took place on April 23, 2010 at the first-ever "Big Four" concert on American soil at the Empire Polo Club in Indio, California.

"The Big Four: Live From Sofia, Bulgaria" was certified double platinum on December 17, 2010 by the Recording Industry Association Of America (RIAA) for shipments in excess of 100,000 copies. (Note: Due to the fact that the set consists of two discs, it was eligible for platinum certification after shipping 50,000 copies; platinum certification for a single-disc release is 100,000 copies.)

According to Nielsen SoundScan, "The Big Four: Live From Sofia, Bulgaria" has sold 134,000 copies in the United States since its November 2010 release.

"The Big Four: Live From Sofia, Bulgaria" debuted at No. 1 on the Billboard "Top Music Videos" sales chart in November with first-week sales of 22,000 copies. The set also debuted at No. 1 in Canada, the U.K. and Austria, while entering at No. 4 in Germany.

"The Big Four: Live From Sofia, Bulgaria" set features full shows from all four bands along with behind-the-scenes and interview footage.