Set of front progressive springs for XB2 and XB4. These springs are shorter with an open end, and have completely different progressive characteristics. The main advantage & benefit of progressive springs is that as the car initially enters the corner the springs work like softer springs to provide maximum traction. As the chassis begins to roll in the middle of the corner, the spring rate progressively increases until it works like a stiffer spring which allows the car to maintain maximum cornering speed. XRAY springs, are manually measured, selected, and matched into pairs to guarantee precisely equal length and damping characteristics. Each spring is laser-engraved with stripes to indicate the firmness, the more strips, the stiffer the spring.
