This is a package of Progressive Rate Shock Springs from Traxxas for use with the Traxxas Ultra Shocks set only. These may be used on either the front or rear of the T-Maxx 3.3 and other specified Traxxas R C vehicles.<br><BR><li>Steel construction.<BR><li>Color  White.<BR><li>Under light duty driving the progressive rate springs soak up small bumps. As the jumps get bigger these springs get firmer the more the suspension is compressed.