These are the optional 12 Coil 3.0lb Pink Shock Springs for the HPI Firestorm, HPIC0510. Constructed of steel, black in color Pink 3.0lb spring rate (pink refers to rate of compression, not color of spring) Two 12 Coil 3.0lb pink Shock Springs for the HPI Firestorm Installation following the model manual Inner Diameter: 0.51" (13mm) Uncompressed Length: 2.2" (57mm) Wire Diameter: 0.04" (1.1mm) The following spring rates are also available; Red 3.6lb (HPIC6912) silver 2.7lb (HPIC8915) White 3.3lb (HPIC6913) Blue 2.41lb (HPIC8916) 5/8/07 OA ir/jxs &