Subs have two length measurements. The first is the Over-All-Length (OAL), this is the length from the tip to tip of the sub - the longest dimension of the sub. The second is the Shoulder-to-Shoulder (S to S) or Working Length (WL), the working dimension of the sub in the drill string. It is measured from the shoulder face of the pin to the shoulder face of a pin on pin to pin subs (1.). On a pin to box sub it is measured from the shoulder face of the pin end to the end of the box end (2). On a box to box sub the OAL and S to S are the same (3).