Sold as 1 piece. Not by dozen. Officially Licensed New Soft Baseball Ball of the National Soft Baseball Federation. As always, it was a general worksman/A, middle school student/B, but both balls are unified and revised to "M". The size is almost the same as a size A, but the weight will be heavier on an average of about 2 grams. Compared to the size B (compared to the size B), the weight is about 0.1 inch (2 mm) larger and the weight is about 0.1 oz (3 g) average weight). The rebound coefficient has been reduced to change the bounce and the dimple shape on the surface of the ball, making it easier to throw and control the ball. As a general professional, junior students are scheduled to be used during the 2017 National Soft Baseball Federation, the 2017 Junior High School Soft Baseball Convention in 2017. Note: The federation may be determined by the ball manufacturer. Please check which manufacturer balls are used by your federation.