This is actually a product I saw earlier this year I have wanted to test. I got a chance to try it at the PGA Show so I got one to do a review of. PuttOut is a company based in the UK and the team was super nice to meet. They have many good products geared towards putting practice and all are practical practice training aids.
The Devil Ball is a training aid that is a type of golf ball that can be positioned for 3 different levels, beginner, Intermediate, and professional. In the package comes two Devil balls, an alignment marker, an instruction card, and a travel pouch. The ball has two different alignments on it. One is a plus sign and the other is just a line. A small part of the ball is nearly flat for the professional version use.
This is a training aid that is both fun and annoying. However, it is a training aid that if used properly can really benefit golfers with their putting. It can help a golfer develop a repetitive putting stroke that creates a square club face at impact. If you do not hit the Devil Ball with a square clubface the ball will roll left or right and give you feedback to know the angle of your clubface at impact. A square putter face will ensure the ball rolls properly and let you know you made a good stroke.
Any practice aid that gives you instant feedback is what every golfer needs. The Devil Ball was fun to try and even though my putting stats are very good I had trouble hitting the Devil Ball correctly. Check out the video below to see the Devil Ball in action.