Worn bumper bellows on your vehicle is more than just an eye sore. These components are part of the protection for the bumper system so the parts, like the shock absorbers for the bumper, can stay rust and debris free that allows them to move just in case of slight contact with a hard object occurs. The bumper bellows are damaged because of their placement on the vehicle. Being on the exterior of the vehicle they are exposed to the environmental conditions along with the UV rays of the sun. Both of these factors play a role into the bellow drying out over time and becoming cracked.
The bumper bellows are made of a long lasting flexible polymer that cover the front mounts, and on most cars the small shock absorbers that connect the bumper to the frame of the vehicle. There are generally two per bumper and can be on both the front and back of the vehicle. In most instances when one of the bumper bellows are noticeably in need of replacement, the others are in a similar condition or not far behind and should also be replaced. They protect the shocks on the bumper from becoming jammed or inoperable due to debris or rust causing the shock to stick in place rather than give when contact is made.
To replace a damaged bumper bellows requires the old one to be removed. They can be help in place with clips or just fitted snugly at both ends of it where it connects to the frame and the bumper. If some of the old component is fused to either end due to heat or time, it has to be removed so the new bumper bellows can be put in place for a solid connection.