The new Ping Putting Cradle for iPhone 4 uses a FREE App to help you develop a repeatable, consistent stroke. Developed by Ping's engineers for all skill levels, the iPING putter app calculates and tracks your Putting Handicap (PHcp) to help improve your putting. All you need is the Ping cradle and an iPhone 4 - the App is FREE on iTunes. Features analysis of your impact angle to improve putting mechanics, classifies your stroke rotation to help match you to the proper putter model for more consistency, and measures the tempo of your stroke to improve control. Can be used with most putters.