Training yourself to make more putts by practicing with a target smaller than a regulation-sized cup is a time-honored technique among golf instructors. It's also the key to the Dead Zero putting aid. The 2 1/8-inch wide disk can be used on a practice green, a carpet or any surface to sharpen your skills from inside 10 feet.
The disk's size is not arbitrary, says Eric Schmitt, Dead Zero's creator. Schmitt performed tests to identify an optimum diameter given the idea that just because you hit a regulation cup with a putt, doesn't mean the ball always goes in hole. Schmitt claims even if struck with just a glancing blow, the Dead Zero simulates a putt that would have been holed in a standard cup.
The Dead Zero Pro ($30) includes a bubble-level on top of the device to help show the slope of the green.