The  Eyeline Bullseye Cup acts as a 30% cup reducer. It is a circular device with a 2 inch opening that visually shows where a breaking putt will enter the hole.Its made of strong light plastic, so is easy to store in you golf bagCan be used on the putting green our on your carpet at home See the Perfect Line with the Eyeline Bullseye Practice Putting CupTo begin, make a few strokes and find the proper line for a breaking putt you are practicing. Take notice of which side of the cup the ball enters the hole. Next, place your Bullseye inside the hole with the opening turned to where the ball will enter the hole. Now, you can visually see the gate where the ball will enter the hole.This will actually give you more hole to aim at when compared to aiming at the lip of the cup. It also helps you visualize the curve of the putt and how your speed will affect that curve.Practicing with the Bullseye Cup will help you visualize the proper line and the proper speed.