I agree with Miller's first post. My opinion is that although the cue ball is near the mouth of the pocket it is still far enough out of it to competently come off the 4-ball and bring the cue ball behind the 12-ball. If I am able to successfully accomplish this shot the following three scenarios could happen. First, I would have broken up the 4-ball/15-ball combination to my opponent's pocket while blocking a "banking 5-ball lane" with the 4-ball. Second, should the cue ball, as it rebounds off the long rail to the short rail and nudges the 12-ball toward the 15-ball, it probably breaks up another easy combination to my opponent's pocket. Third, and most importantly, my opponent is trapped behind a ball and has no clear shot to his pocket.