Swingweight or MOI?

Swingweight of a golf club is a measure of mass distribution around a fulcrum point located 14 inches from the grip end. An arbitrary scale of letters and numbers (e.g. C6, D2, etc) indicates the swingweight. 

MOI of the golf club is a measure of the resistance the club when swinging it around an axis of rotation located at the grip end. It's a indication of the energy required to swing the club.

Both swingweight and MOI give a sense of how the clubhead weight feels in relation to the length of the club during the swing. When the swingweight of all clubs in a set is constant the long irons will have a heavy head weight feel and the short irons will have a lighter head weight feel.

When a set is MOI matched, the head weight/length feel relationship is reversed -- short irons have a heavier head weight feel than long irons. MOI-matching makes long irons feel easier to swing than swingweight matching. MOI-matching yields an improved sense of control with the short irons. MOI-matched irons promote greater consistency in the swing through the set.

The great majority of golfers who compare the feel of a constant swingweight-matched set vs. an MOI-matched set in blind testing find MOI-matched clubs have a more consistent swing feel through the set. They prefer MOI-matched sets over swingweight-matched sets for their game.

We see the preference for MOI-matched iron sets in golfers of all skill levels and handicaps. The preferred MOI varies for each golfer -- clubfitting identifies the preferred MOI for each golfer. An MOI vs. swingweight test can be done by any golfer with their own set using lead tape to change head weights on their irons. 

Retail "off-the-rack" iron sets are built by the OEMs to have constant swingweights. It's done for easier bulk manufacturing and to simplify inventory stocks for retailers. Essentially, iron sets are built for the convenience of the OEM and the retailer, not for the performance preference of the golfer.

The MOI-matching option can be a significant benefit of custom iron and wedge sets. A professional fitting process identifies the optimum MOI match to your swing, then the set is built to match your swing specifications. MOI-matched clubs make it easier to achieve swing consistency, a key frontier for reaching lower scores.