The Bobby Grace Face Off Putter comes with two inserts that players can use to customize the feel of the putter depending upon the speed of the greens and personal preference. There’s a polymer face for a soft feel, and a titanium one for a harder feel.
Both faces offer what MacGregor golf calls Distance Corrective Technology. This is supposed to help impart the same forward energy to the ball, regardless of where on the face contact is made. That should help to make putting more consistent.
Remember, though, that changing the face of the putter in mid round violates the rules of golf.