The R9 Supermax Iron features long and mid irons with a 2 piece undercut cavity design and shorter irons in a 1 piece design with no undercut. The long irons feature a 17-4 body and a custom 455 face while the 8 to wedges are all 17-4 SS. The irons do have some offset especially in the longer irons which becomes progressively less as the irons get shorter. The lofts are ultra strong with a 23* 5 iron again showing a big focus on distance. This is not a tradition undercut in that it has an open pocket cavity. It is in fact a hollow cavity and face filled with foam and a plug behind the sweet area of the face. These features are used to create vibration dampening and soften the feel at impact. The back cavity is pretty good looking and does feature TM's inverted cone technology.