Cocktail shakers were used on convertibles. They reduce vibration that was the result og a non-rigid top. There are two in the rear (50 lbs each) and two in the front (25 lbs each). I believe there is a difference in mounting between years..at least 67 and 68. My bird was missing the two in the rear so I salvaged a pair from a 67 Camaro and they did make a difference in the ride.
