Ultra Shocks Progressive Rate Springs (4) 4957R
Springs, progressive rate (for Ultra-Shocks only) (progressive rate) (f/r) (4)
Under light-duty driving, the progressive rate springs soak up the small bumps as a softer spring would, but when the conditions get rough and the jumps get big, the progressive rate springs step up to the challenge by getting firmer as the suspension is compressed. This resists the chassis from bottoming out from jumps to keep the chassis under control.
Accessory part for these models: