Callaway Big Bertha 08 Individual Iron (4-Iron) Fully integrated set design provides seamless performance progression with consistent distance separation and optimal trajectories. New i-brids blend the control and accuracy of irons with the forgiveness, distance and versatility of hybrids. Super game-improvement mid and short irons deliver the ultimate in forgiveness with increased offset, a large effective hitting and a constant width sole. Callaway Golf Core Technologies include Extreme Notch Weighting , VFT, S2H2 and a 360-Degree Undercut Channel. The New Modified Tru-Bore , an advanced version of the original Tru-Bore design, incorporated a polycarbonate tip plug at the end of the shaft that dampens vibration for enhanced feel and performance.