An arm ball is a type of delivery in the sport of cricket. It is a variation delivery of the cricket ball by an off spin bowler.
In contrast to an off break, an arm ball is delivered without rolling the fingers down the side of the ball on release. This means the ball has little or no spin on it, and it does not spin appreciably off the pitch. Instead, it travels straight on "in the direction of the arm" - from which it derives its name.
The arm ball is best used as a surprise variation by a bowler who is turning his off breaks considerably. A complacent or poorly skilled batsman playing for the expected spin can be taken by surprise and end up edging the ball with the outside edge of the bat, possibly offering a catch to the wicket-keeper or slips fielders. Saqlain Mushtaq and left-armer Daniel Vettori use the arm ball to good effect.
See also