The STABILITY shaft has made quite a difference for a lot of players.
"That shaft with the ER9 are an unstoppable duo... I have never putted this well in my life. Had it at a 4 day golf trip / friendly tournament and had the most consistent putting weekend of my 30+ years of play. Consistent distance control and tracked true... the ER9 does take some getting used to on putts over 15’, so all distance issues were putter head related (and my time with it) than shaft. Very happy". Vincent C., New Jersey, USA