Most BBCOR bat manufacturers list BBCOR barrel at 2 5/8”, but it's important to note all BBCOR bats are slightly under 2 5/8” size to pass the NFHS/NCAA barrel test and due to manufacturing tolerances. When comparing it to some of the more popular BBCOR models in the market, the Alloy XP is only 0.05” smaller. For perspective, that is about the thickness of the plastic wrap on most bats. It’s bigger than wood bat barrel diameters, which most BBCOR guys are comfortable swinging and making contact.
USSSA XP Bats feature a 2-3/4" Barrel.