Targeted at the open wheel modified racing market, this shock promotes better feel and improved grip. The smaller 1/2" (12.7mm) shaft displaces less oil when compressed, giving the shock an added advantage of less rod pressure gain, thus improving driver feel. IMCA Legal gas pressure shock. Performance at its best on fast or rough tracks. Bodies grooved for coil-over applications. Available in 5/8” shaft upon request.How to read and specify your part number: The first two digits are the shock series (example: 73), the third digit is the stroke length (example: 9), the fourth digit is the compression range (example: 3), the final digit is the rebound range (example: 5). Questions? Contact us at 800-632-2320.