H&R 2.50" I.D. Race Springs are made with extremely high tensile strength wire alloy which allows the use of a thinner wire. Manufactured using advanced materials and precision technology in Germany, H&R 2.50" I.D. Race Springs are crafted from special lightweight (hf) 54SiCr6"spring steel. For any given spring rate, they are on average 15% lighter and have 10% more travel than competitors' springs. Main springs range from 6" to 18" in length and are available in a wide selection of spring rates. TENDER SPRINGS: H&R 2.50" I.D. Tender Springs are made of trapezoidal (flat rather than round) spring wire and have a low block height for maximum travel. These springs are designed for demanding motorsport environments, and like all H&R springs, have been pre-blocked at the factory so they will never set or sag. The H&R 6"mm I.D. Race Spring line is crafted from special lightweight (hf) 54SiCr6"spring steel and is the most comprehensive 6"mm I.D. Race Program in the U.S. If you own a Porsche GT3 or another Euro spec car, our range of 6"mm I.D. Race Springs has you covered. With hundreds of main springs and tender springs available, H&R has the lengths and rates necessary for optimal tuning and setup. The H&R complete line of 6"mm I.D. main springs range from 80mm to 300mm (25.4mm = 1 inch) in length and 25 N to 700 N (N/mm x 5.709 = pounds/inch) spring rates.