Eibach ERS 4.00 in. Length x 2.00 in. ID Coil-Over SpringEibach's ERS line has evolved over the years to be the world's most prominent, comprehensive and superior Race Spring System. Eibach Race Springs are all manufactured in series production, often repeated, with a strong manufacturing experience. Thus, Eibach constantly achieves the most linear spring characteristic (rate) while maintaining the lowest tolerances and the highest quality in the industry.