This set includes 3 impact ball liners with a matching marker, designed as a precision putting alignment tool for golf. The easy-to-use stencil lets you quickly draw clear accurate lines on your golf ball to align your putter face and target line perfectly. It is USGA legal and can be used in official competitions, and is trusted by many tour players for putting practice and games. Made of durable plastic, it fits standard golf balls, ideal for indoor putting practice, outdoor golf course training and official rounds to improve putting accuracy.