Product Description For these irons, the sole objective was consistency. Z 355 irons are packed with technology designed to deliver incredible distance and accuracy with every swing. Action Mass - A heavier head weight plus an ultra-high balance point combine to deliver incredible consistency with maximum distance and forgiveness. Optimized Set Construction - A two-piece construction in the 4-7 irons - a powerful HT1770 maraging steel face and resilient 17-4 body - and one-piece, softer 431 steel construction in the 8-iron through approach wedge offers full set playability and versatility. Tour V.T. Sole - A high-strength maraging steel face maximizes distances and forgiveness without compromising feel Larger Sweet Spot - A higher hosel section allows for an expanded face area, which creates a larger sweet spot.