HiBore XLi incorporates some current HiBore features (hollow heads throughout the set) with a few new wrinkles of its own. For starters, each iron is better equipped to handle its specific role. Hybrid-like long irons (3 and 4) are more forgiving (higher MOI) than HiBore due to a bigger chassis and squarish shape. Plus, the short irons are more nimble (though they won't be confused with blades) because of a more compact head, shorter blade length and thinner topline.