Research shows that over 70% of all golfers incorrectly align their putts. Use of this device can greatly increase your accuracy and proficiency on the putting green. These units will work on most putters (10mm maximum shaft size) and project a red dot where you aim to more accurately define your putting line. They aren't as visible in bright sunlight, shaded areas or indoor practicing is more ideal for this type of item. For better visibility in brighter conditions, I'd recommend using the green putter laser which is available in my other listings. When using on center shafted putters, you just have to compensate for the slightly different positioning of the putting line due to where they're mounted. The picture below will vary in size depending on your screen resolution that you're running your monitor at, they may appear even larger if you're running a lower screen resolution. Please read below under the features area for the exact measurements of this item. These are perfect for golfers who wants to help improve their golf game, and work mainly on right handed putters only. These can retail for as high as $49 each, but buying in large quantities allows me to pass the savings on to my customers and offer them at a greatly discounted WHOLESALE price. I have these custom made directly from the manufacturer, so my prices and quality can't be touched. Don't settle for bulky outdated models at higher prices, get the smallest, best designed units around, which you'll find here at Genaldi.com!