Callaway X2 Hot Irons Iron Set Deep Central Undercut: The New Deep Central Undercut increases the rate the face flexes and rebounds Stabilizing Arch: Exceptional sound and feel at high ball speeds come from a stabilizing arch that reinforces the face Lightweight Shaft Options: Lightweight Speed Step 85 steel shaft available in regular and stiff flexes A new lightweight graphite shaft offering brings great feel and control with higher launch angles Increasing ball speeds to make this iron even longer