Have you ever wanted to let loose with a chainsaw on your golf ball? Paul Nagi did just that, and invented a useful training aid in the process.

Called “The Pill,” it’s a golf ball with two “sides” sheared off. (Nagi carved the prototype in his garage.) When placed so that it stands up on the line of a putt, “The Pill” will only roll properly if struck squarely. Hit it off-center or with an off-line stroke, and the ball will wobble and topple over.

You can also use “The Pill” for chips and longer shots, though it works best as a putting aid. Nagi’s invention gained lots of attention at the 2013 PGA Merchandise Show, and it’s earned publicity from Golf Digest, Links Magazine and MyGolfSpy.com, among others.

“The Pill” retails for $12.95 apiece, making it one of the more affordable training tools on the market.