Guerin Rife IMO Training Putter:

The best way to demonstrate Guerin Rife's IMO putter's weighting concept is by having golfers putt with this IMO Trainer. The Trainer is simply an identical version of the center weighted portion of the IMO putter without the darker hollow side wings. Therefore 100% of the head mass is directly behind and inline with the swing plane. Back in 1934 the USGA began requiring putter head designs to have a greater length from heel to toe than from front to back. The basic reasoning being that a putter with the inline elongated head shape was too easy to use—like a croquette mallet. The IMO Trainer allows you to easily understand and experience the benefit of center mass weighting.