One of the most significant putter head design features is the Moment of Inertia (MOI) of the putter about its vertical Center of Gravity (CG) axis
. The MOI about the vertical CG axis is the design parameter indicating how far the ball will travel when impact occurs off-center as compared to the distance for a putt hit on-center at the same stroke speed. The higher the MOI, the more resistance to twisting on off-center hits.