This is a set of 12 used DUNLOP FORT hard tennis balls. They were used in lessons once a week for six months, so the "T" is written on the balls. These are especially recommended for seniors in the beginner/intermediate class, for ball feeding for elementary and junior high school students, for serve practice, and for warm-up balls. They can also be attached to the legs of chairs to prevent scratches. The firmness is just right for massaging your lower back. Price reduced.