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An outswinger is bowled by holding the cricket ball with the seam at an angle and the first two fingers running along either side of the seam. Once the ball has worn and been polished so that one side is rougher than the other, the rough side is placed on the left (as seen from the bowler's viewpoint). When the bowler delivers the ball, he angles the seam so that it points slightly to the left as well, and releases the ball rotating about a vertical axis with the seam along the rotational axis. The angle of the seam to the direction of motion produces an aerofoil effect as the ball moves through the air, pushing it to the left. This is enhanced by differential air pressure caused by movement of air over the rough and smooth surfaces, which also tends to push the ball to the left. The result is that the ball curves, or swings to the left.
From a right-handed batsman's point of view, the swing is away from his body towards his right, i.e. towards the off side. This swing away from the body is the source of the name outswinger. To a left-handed batsman, the swing is in towards the body and towards the leg side which from a technical point of view makes the outswinger, now an inswinger.
Outswingers may be considered to be one of the more difficult fast deliveries for a right-handed batsman to play. This is because the ball moves away from his body. This means that any miscalculation can result in an outside edge off the bat and a catch going to the wicket-keeper or slips fielders.
To a right-handed batsman, a fast bowler will generally concentrate on bowling repeated outswingers, aiming to tempt the batsman to play away from his body and get him out in one of the ways described above. However, sometimes a fast bowler may attempt to deceive the batsman by bowling an off cutter instead of a standard outswinger, and look to get a batsman out either bowled or lbw. More commonly, variation is in the length of the ball, with yorkers and bouncers.