The 5551 is an asymmetric four
ball pattern in which three normal Cascade throws are followed by a quick
horizontal pass. The speed of this pattern closely matches that of the Five
Ball Cascade; as such it is most often learned for the sole purpose of practicing
To learn the 5551, it is best to start with two balls in each hand. Make a throw from your dominant hand, followed by a throw from your non-dominant hand, then another throw from your dominant hand. This should leave you with three balls in the air, and one ball in your non-dominant hand. Just as the first ball is approaching your non-dominant hand, make a horizontal pass to your dominant hand, and catch the first ball in your non-dominant hand. Then catch the remaining balls.
Once you have this mastered, all that's left to run the full 5551 is to make another Cascade-like throw using the ball that was just passed to your dominant hand, thus repeating the whole cycle over again. Since this trick is asynchronous, you can also learn the 5551 using your dominant hand to make the passes.