Skyjacker Nitro Shock Absorber 1987-1987 GMC V1500 PickupSkyjacker(R) Suspensions offers you a high quality shock absorber with true velocity sensitive valving. Shock absorbers, or spring dampers as it is called everywhere else except in the U. S., control the rate at which suspension springs compress and rebound. As the shock is pushed together, this is called bump or compression. As the shock expands, this is called rebound or extension. Absorbing the shock' of bumps and suspension loading is actually