Eibach Competition Springs are used by top race teams, from F1 to WRC, from Le Mans to NASCAR. To produce springs with unparalleled precision and repeatability, Eibach uses the world's finest Hi-Ten spring steel, produced to exceedingly precise tolerances-according to Eibach specs. Eibach use world-renowned German CNC coiling machines, as well as many other machines engineered and built specifically by Eibach. In short, Eibach use state-of-the-art technology, in every step of the manufacturing process.2.25" (57.15mm) Internal DiameterUnique alloy (Eiballoy) maintains spring rate throughout life of the spring.Shot-peened for long life.Phosphated and epoxy coated for corrosion protection.Designed to give maximum spring travel at short spring lengths.Ultra lightweight for reduced unsprung massExceptional block resistance and durabilityPrecision tolerances - the tightest in the industry precision plan parallel and square end configurations under unloaded and loaded conditions to +/- 1 degr