This damper set combines ease of use and performance. Damper cylinder is TRF (TOPLINE) size. We recommend using a piston with an outer diameter of 0.39 inches (9.9 mm). Set Contents: Damper cylinders (hard anodized aluminum) x 4, damper top caps (aluminum) x 4, cylinder nuts (resin) x 4, damper end caps (aluminum) x 4, shaft guides x 4, spacers x 4. *Please purchase the following parts separately. Damper Top, Spring Retainer, Damper End, Diaphragm, O Ring for Damper, Damper Shaft, Spring