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. Rebound Frame technology helps you generate incredible ball speed, while the signature lightweight swing feel of XXIO lets you do it all with remarkable ease. Experience the Difference. 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. Titanium Faces The thin, high-strength titanium face, along with hollow portions of the heel, allow for an even larger high-density tungsten-nickel toe weight. This toe-side weight optimizes the Center of Gravity location for a higher, straighter launch. In addition to the L-Shaped Groove at the bottom of the Iron body, new grooves in the outer periphery of the clubhead improve face COR to add ball speed and 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. Weight Plus XXIO's proprietary design positions mass in the butt-end of the shaft, under your grip and behind your hands. This counterweight provides an easier takeaway, helps you find the ideal spot at the top of your swing, and makes it easier to release into the downswing for more consistent contact. Optimized CG By Loft XXIO 13's progressive variable face thickness optimizes speed and launch for each loft. Long Irons are designed for carry, with a lower Center of Gravity to provide enhanced ball speed right where you strike the face. Short Irons emphasize control, with a slightly higher Center of Gravity for better high-low MOI.