This spring is a 315lb rated spring that fits 1963-77 Corvettes. Please verify bolt size before ordering as the 63-77 Corvettes should have 9/16" bolts with a 13/16" hex head mounting the spring to the differential cover. As patent holders of the TRW designed Composite Transverse Leaf Spring, Muskegon Brake ensures a quality product and a superior ride when you purchase your new, innovative composite spring. State of the art technology was a major component of this spring. In order to preserve the excellent handling associated with the Corvette, Muskegon Brake offers this spring for 1963-1982 Corvettes. This is considered the master upgrade for the Corvette suspension for ride and performance. Each composite spring is accompanied by all the necessary mounting hardware, including spring bolts and a special heat shield.