The M-15 is the more forgiving half of Mizuno's new Modern Series, which sits alongside the Signature Series blades rather than replacing them. The M-13 is the tour-shaped one; the M-15 is the one most good golfers should actually be looking at. Through the 4 to 8 irons it's a hollow-body build with a Grain Flow Forged 4135 Chromoly face and a stainless back piece, tungsten weighting suspended inside the head — 51g in the long irons, a shade over 50g in the mid irons — and a multi-thickness face Mizuno calls the Contoured Ellipse. In plain terms: it launches higher and holds its line on a miss far better than the shape suggests, and the set blends progressively rather than turning into a different club at the 7-iron. It finished runner-up in MyGolfSpy's 2026 Most Wanted players' distance test and made Golf Digest's 2026 Hot List, and the performance case is not really in dispute. Feel is where the published verdicts split: Golf Digest's panel reported a soft, satisfying strike, while Plugged In Golf found it loud and hard away from centre and Golfmagic thought the M-13 the better-feeling of the two. That disagreement is the most useful thing to know before you buy — this is a hollow-body iron, and if buttery is the reason you buy Mizuno, hit both. Two other honest caveats: testers consistently report the carry gain showing up in the mid irons more than the long ones, so it isn't the biggest long-iron jump in the category, and it is sold per club, which makes a full set expensive.