Used to have an Agitator, the top shock was an oversized damper tube. The main body was a delrin tube, closed at one end with a lip for a spring perch. I don't remember if you used a collar or spacers to adjust ride height. The piston was a nylon rod about 3/8ths in diameter and maybe 1/2 inch long. Bob is right, ball cups at both ends. The larger diameter compared to side damper tubes gave extra and more consistant damping. Unfortunately I too got rid of mine long ago.