Traxxas Spring Retainers for Traxxas Shocks. This set contains the spring retainers that hold the springs place over the shock body and the piston heads that control the amount of oil flow in the shock cylinder. Constructed of molded plastic. Contains enough parts for two shocks. Fits the shocks on most Traxxas nitro and electric powered vehicles. Two hole piston head for greater dampening or three hole piston head for softer spring performance. INCLUDED: One Traxxas Spring Retainer Set with: Two upper and two lower spring retainers Two 2 hole piston head covers Two 3 hole piston head covers Required Parts Disassembly of shock to install parts.