The main advantage and benefit of progressive springs is that as the car initially enters the corner they work like soft springs to provide maximum traction. In the middle of the corner, the spring rate progressively increas until they work like a hard spring that allows it to maintain max cornering
Like all the other XRAY springs, these XB4 springs are manually measured, selected and matched into pairs to guarantee precisely equal length and damping characteristics. The springs have been specifically designed to complement the big bore shocks. Set of 2.