Ultimate-match coil shock springs for pan cars and formula front suspension offer an additional range of choices to fine-tune your car. Powder color-coded for quick & easy identification. Black color. C=2.5 (soft). Set of 2. Developed through extensive testing and racing experience. Stiffness is controlled by the thickness of the wire and the number of coils; softer springs have a lower ''C'' value, stiffer springs have a higher ''C'' value.