We tested: 4-Gap in Nippon N.S. Pro 1030 steel shaft
Company line: "The undercut cavity and mid-width sole increase forgiveness and playability. A urethane insert in the cavity dampens vibration and softens feel. The N.S. Pro shaft increases launch."
Our Test Panel says: Reliable but lacks 'wow' factor; heavy bottom weighting and sole help to handle the rough; favors shock absorption over providing mis-hit feedback; elliptical groove pattern is a somewhat useful aiming device; progressive offset and heel weighting help to take right side out of play.
Good distance control and high, repeatable ball flight. Mike Gorski