The hydraulic cylinder is what raises the convertible top on your Mustang. Over time the seals become weak causing leakage and the Mustang convertible top is slow to raise and lower. Two cylinders are needed per Mustang.
1983-1993 Mustang Convertible Top Cylinders
1994-2004 Mustang Convertible Top Cylinders
This is my almost all original 1989 GT. It has a 4.10 and glasspacks. That is, as far as I have found, the only unoriginal items.
I had been looking for a FoxBody to call mine for about ten years....