Suspensions bushes are under a lot of stress. Bushes insulate the vibrations and noises from the chassis, and also absorb the hardest shocks so parts wont break. The bushes need to be strong enough to prevent un-wanted wheel movements, but soft enough to be able to absorb the shocks which could break things.
Powerflex is the De-Facto manufacturer for aftermarket polyurethane bushes. They are available quickly and with great prices from our stocks.