My favorite ab workout

Here's my favorite ab workout.  Try this one and you will really feel it work!

Sit with your feet on the floor, knees bent.  Sit back at a 45 degree angle.  Then hold a 5 to 10 lb weight and start holding weight in front of you holding it with both hands and arms straight, then move the weight towards the ground on your left side, come back to center, move the weight to the right side.  Repeat for 15 times on each side.  Once you have finished your first set of 15 on both sides, I do 35 crunches, then repeat the previous workout.  I do each for 3 sets.