Callaway’s GBB Epic Sub Zero driver — the more forgiving, yet deeper-faced option in the GBB Epic driver series — has made waves on professional golf Tours, and it also garnered the most votes in GolfWRX’s Members Choice: The Best Driver of 2017. The retail models measure 460cc, but there’s another 440cc version floating around on Tour in the bag of Alex Noren.

Now, there’s yet another GBB Epic Sub Zero model in existence; a “GBB Epic Sub Zero PM440″ is listed on the USGA Conforming Clubs list.20160753

Screen Shot 2017-06-02 at 11.46.02 AM

What could a left-handed Callaway driver named “PM” possibly mean? We’ll go out on a limb and guess that Callaway has made a GBB Epic Sub Zero 440 driver especially for Phil Mickelson, but we will update this story when Callaway representatives provide further insight on the “PM440.”

Update: “It’s a left-handed 440cc version of Phil’s driver,” said a Callaway representative. “It’s a one-off Tour prototype that they built of his driver for him, instead of the standard 460cc head.”

Discussion: See what GolfWRX members are saying about the GBB Epic Sub Zero drivers in our forums

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  1. Personally I lprefer a smaller head like a SLDR/M1 430/440, 917 D3.

    But I really wish a there was a pic from the address point of view, because that’s really a huge factor of importance I think.