Perfect your polisher with a counterweight. The Porter Cable 7424 Dual Action Polisher is designed to move both in an orbital motion and a jiggling motion. With all that movement, the polisher may become unbalanced and the user has to compensate for the added wobbling. This problem is easily corrected with a counterweight. The counterweight fits on the eccentric housing, located just above the backing plate. This is the part that causes the plate to spin. The semi-circular weight spins with your backing plate to balance out any irregular motion and make the Porter Cable operate more smoothly. With the addition of a counterweight, your Porter Cable 7424 will work like a charm and render a perfectly uniform finish every time. The counterweight is for use with a 6Â” backing plate only.