Guerin Rife TwoBar Hybrid Mallet Belly Putter:

The TwoBar Hybrid Mallet Putter features an innovative aluminum and polymer insert. The 6061 aluminum face is CNC-milled and features Rife Putter's patented RollGrooves. The back of the face is made of a high durometer (responsive) polymer that is bonded to the aluminum under high pressure to create a solid, unitized insert. The combination of the gripping effect of the RollGrooves and the responsiveness of the polymer gives the golfer a whole new level of distance control.

RollGroove technology: These are horizontal, very closely spaced grooves. The space between these grooves is called land. Because this land is sharp, the ball tends to spend more time on the face at impact. This allows for only one to two degrees of loft instead of the four degrees on conventional flat-faced putters.