An iron set assembled from two or more different models — typically forgiving cavity backs or hollow-body heads in the long irons, compact players irons in the scoring clubs. Also called a blended, split, or mixed set. This is not exotic: roughly three-quarters of tour players blend models, and modern lines like Titleist's T-Series are designed to be mixed. The one trap is gapping — consecutive irons should sit 3–4° apart in loft, and different models rarely share loft specs, so an unchecked blend can leave two clubs flying the same distance. A launch-monitor session mapping carry numbers across the seam is the clean way to prove the blend before you trust it.