I have PXG Gen 2 irons with the Aerotech Steelfiber shafts. I replaced those recently with the MMT when I upgraded to Gen 5 irons. I love the MMT shafts and can definitely feel the lighter weight. Not that I didn't like to Steelfiber shafts and had originally planned to use them on my Gen 5 irons until I tried both side by side. You won't go wrong with either, but I would recommend the MMT. I am 66 years old and play to an 8 handicap.