Actually... springs are not adjustable. You can alter the ride height by changing the position of the lower mount. A threaded body coilover has the benefits of 1 piece body/adjuster construction, and in some preload capability and shock stroke adjustment. In some cases, the increased shock body size allows for a larger shock piston diameter that can be used for improved flow control, and greater damping force than can be attained with the stock-diameter body. Ground Control coilover sleeve setups can work VERY well if you complete the package with quality shocks and allow you to use custom spring rates to suit your personal needs. In addition, most if not all are designed to work with Koni Sport shocks which can be custom-valved or rebuilt with ease here in the US.