Energy Suspension 4.2131G Front Spring Shackle ONLY Durability is superior for cars, trucks and SUVs; road salt, oil, and a host of other common under car contaminants will eventually destroy the rubber bushings on your vehicles, not to mention the weight and torque forces that typically compress rubber Hyper-Flex replacement polyurethane components stand up well to contaminants that often destroy rubber and have been engineered to give longer-lasting performance and not compress permanently Hyper-Flex is offered in a variety of durometers (firmness or softness), depending on product application; performance tested and race proven; used for all of Energy Suspension products that require a higher level of performance and durability If you are modifying, building a new vehicle for scratch or restoring an old one, Energy Suspension's Hyper-Flex performance polyurethane should be the 'ground zero' focus of your present and next vehicle plans Over two decades of in-house experience in innovating, engineering and formulating wide selection of polyurethane components for many different industries, Energy Suspension has qualified as premier manufacturer of the high quality polyurethane products Durability is superior for cars, trucks and SUVs; road salt, oil, and a host of other common under car contaminants will eventually destroy the rubber bushings on your vehicles, not to mention the weight and torque forces that typically compress rubber Hyper-Flex is offered in a variety of durometers (firmness or softness), depending on product application; performance tested and race proven; used for all of Energy Suspension products that require a higher level of performance and durability If you are modifying, building a new vehicle for scratch or restoring an old one, Energy Suspension's Hyper-Flex performance polyurethane should be the 'ground zero' focus of your present and next vehicle plans Over two decades of in-house experience in innovating, engineering and formulating wide selection of polyurethane components for many different industries, Energy Suspension has qualified as premier manufacturer of the high quality polyurethane products