The Eibach ERS (Eibach Race-Spring System) Metric Coil-Over Springs rely on a Main and Tender spring concept that provides a softer initial rate when both springs are compressed together. Then delivers the desired firmer ending rate once the tender spring compresses completely. This design allows you to fine tune your suspension for the handling and ride for each track. An endless variety of metric spring combinations allows you to give your car the grip it needs for ultimate traction exiting corners and during launch, while also allowing you to give your car the stiffness it needs to reduce body roll and provide enhanced steering response. Available in progressive spring rates to double and even triple your spring rates, the ERS Metric spring system will provide every advantage you need to dominate at the race track.