The Cleveland CG4 irons represent Cleveland's first foray into game-improvement irons made with light density CMM brand metal. Cleveland Golf's proprietary CMM metal was the industry's first light-density steel and is the same material used in CG10 wedges, as well as CG1 and CG2 irons. This revolutionary new material contains microscopic carbon spheres that are suspended within the metal to help create a matrix material that is 10% less dense and 15% softer than the traditional carbon steel used in cast and forged clubheads. The light-density properties of CMM metal allowed designers at Cleveland Golf to redistribute 25 grams of discretionary weight to the most critical areas of the clubhead for optimum performance. CMM metal contains 17 times more carbon than traditional carbon steel, which not only leads to greater vibration absorption, but also gives these irons a softer feel at impact. The overall design of the CG4 irons, combined with the benefits of CMM metal, has helped create irons with an exceptionally low and deep center of gravity (CG) and a moment of inertia (MOI) that is higher than any other iron in its class. The wider sole and cavity-back design of these irons also gives them both increased stability at impact and an even larger sweet spot for added forgiveness on off-center shots.