In baseball, an off-speed pitch is a pitch thrown at a slower speed than a fastball. Breaking balls and changeups are the two most common types of off-speed pitches. Very slow pitches, those which require the batter to provide most of the power through bat speed, are known as "junk" and include the knuckleball and the Eephus pitch, a sort of extreme changeup. The specific goals of off-speed pitches vary, but all are used to disrupt the timing of the batter, lessening his chances of hitting the ball solidly, or making contact with it at all. Virtually all pitchers have at least one off-speed pitch in their repertoire. Despite the fact that most of these pitches break in some kind of way (to the sides, down, late on its path or gradually,...), batters are sometimes able to identify them due to many hints the pitcher gives: arm angle change, arm speed change, placement of fingers and many others. It is unknown whether off-speed pitches affect batting averages.