SPECIFICATION: Front Spring rate: 10 kg/mm (560 lbs/in) & 8 kg/mm (448 lbs/in). Under 600,000 times continuously test, the spring distortion is less than 0.04%. In addition, the special surface treatment improves durability and performance COMPATIBILITY: The coilovers shock absorber replacement For BMW 3 E90 2004-2011 326i,328i,320i,323i,325i,328i,330i,335i,316d,318d,320d,325d,330d,335d. Replacement For BMW 3 E91 2004-2012 326i,328i,320i,323i,325i,328i,330i,335i,316d,320d,325d,330d,335d PREMIUM MATERIAL: The coilover comes with 6061 aluminum alloy with T6 for increased hardness, high quality precision parts, high strength and durability. It is fully loaded and safe for installation. FUNCTION: Coilover Struts Shocks Easy to control, significantly improves stability when bumping or cornering, effectively dampens driving vibrations and improves ride comfort under difficult road conditions and heavy loads. DOUBLE TUBE CONSTRUCTION: The double-tube structure has a longer travel, with higher height adjustability, by reducing the pressure of the mechanical structure, reducing more friction to obtain a longer travel and improve the driving experience Coilover Suspension Spring Struts Replacement For BMW 3 E90 2004-2011 Replacement For BMW 3 E91 2004-2011 Height Adjustable Shock Absorber