Conventional Springs are high-performance, aftermarket suspension springs primarily used in motorsports and motor racing. The OD (outer diameter) size and free length, along with Hyperco’s Dynamic Travel Response™ spring design, allow for optimization of the total vehicle performance on many Circle Track vehicles and applications. Unlike Coil-Over Springs that are available in a multitude of free lengths, Conventional Springs are limited in their free length offerings, often as a result of the sanctioning bodies and rules. The Engineers at Hyperco decided to analyze the dynamic characteristics essential to Conventional Spring performance. That data resulted in the development of the Dynamic Travel Response spring design concept. Working within the limitations and rules, the Dynamic Travel Response design allows all springs to exceed the performance requirements for travel and rate linearity, and is still designed with significantly less physical weight 5.5 Inch OD Rear SNP-Series Street stocks & Stock Appearing Conventional Springs SNP12 Series. 12" free length. 5.5 Inch OD. One end pigtail, one end closed. Spring rates from 175 lb per inch to 300 lb per inch. High tensile chrome silicone material. Semi-gloss black powder coat for OE appearance. Rear suspension setup for circle track racing.