The all-new XXIO 13 Irons deliver the ultimate in moderate swing speed performance. Their advanced, four-piece design has a remarkably low Center of Gravity for a satisfyingly high launch. 4-PIECE CONSTRUCTION XXIO 13 Irons feature a low Center of Gravity thanks to their 4-piece construction, which uses titanium faces and tungsten-nickel sole weights. That weighting, combined with our unique Rebound Frame structure which alternates stiff and flexible zones for added ball speed, gives you a satisfyingly high launch with incredible distance. REBOUND FRAME Rebound Frame uses alternating layers of stiff and flexible zones to enhance overall COR, creating an effect that acts like a spring within a spring. It adds ball speed and distance to every shot. On the Irons, a thinner face flexes more extensively while perimeter grooves etched deep into the interior of the Iron body add even more flex, especially for shots struck low on the face.