Mizuno Nighthawk Baseball Bat (-10) New Patented 2 PC Link Construction: Hybrid Construction combines an Alloy Barrel with Composite handle for flex and lower MOI. Variable Wall thickness Technology: By adjusting the wall thickness in various locations of the barrel we are able to increase performance creating a massive sweet area. Single wall aluminum ally barrel: Great Performance & Sound. Approved for USSSA Barrel Diameter: 2 3/4"