The rear shock provides two basic functions: Supporting the weight of the rear of the bike with a bump-softening spring, and controlling any up-and-down oscillations of the suspension by providing damping. Rear shocks consist of two telescopic tubes which slide into each other, a spring of some type and an eye at either end through which the whole mechanism is affixed to the frame. A small bushing (a type of simple bearing) in each eye enables the shock to pivot smoothly when the suspension is active.