These Spring Compression Shocks are loaded with spring steel coil springs and a metal shaft. They're responsible for controlling compression, bounce, roll, travel and ride type. These are essential to the driving and keeping the suspension set up. These are usable for both the front and rear. The Spare Parts Baggie comes with several Shock spring compressors, so you can stiffen the front or rear Shocks up a little, as you feel the need.